I am Raghuveer

In my opinion programming means thinking, and it is fun. My vision is to teach programming in more understandable manner to the students from rural background. I support programming for everyone

Showing posts with label C#.NET. Show all posts
Showing posts with label C#.NET. Show all posts

Generate unique random string with desired length using GUID

GUID, also known as Globally Unique Identifier, is an 128-bit integer (16 bytes) that can be used to uniquely identify a record in the database (other than the auto-increase number). It is best used as a primary key as well.
But in some occasion, what you need is not really a GUID, but a random string that is "unique enough" to be used by your system. And you might want to store it as a string in your database (for whatever reason).
In C#, you can do this by using the GUID hash code. Here is the function that returns a "unique enough" string with a desired length:

        /// <summary>         
        /// Gets a unqiue key based on GUID string hash code.
        /// </summary>
         /// <param name="length">The length of the key returned.</param>
         /// <returns>Unique string</returns>
         private static string GetUniqueString(int length)
         {
             StringBuilder uniqHashKey = new StringBuilder();
             while (uniqHashKey.Length < length)
             {
                 // Get the GUID.
                 uniqHashKey.Append(Guid.NewGuid().ToString().GetHashCode().ToString("x"));
             }
             return uniqHashKey.ToString();
         }

Creating a Data Access Layer (C#)

Introduction

As web developers, our lives revolve around working with data. We create databases to store the data, code to retrieve and modify it, and web pages to collect and summarize it. This is the first tutorial in a lengthy series that will explore techniques for implementing these common patterns in ASP.NET 2.0. We'll start with creating a software architecture composed of a Data Access Layer (DAL) using Typed DataSets, a Business Logic Layer (BLL) that enforces custom business rules, and a presentation layer composed of ASP.NET pages that share a common page layout. Once this backend groundwork has been laid, we'll move into reporting, showing how to display, summarize, collect, and validate data from a web application. These tutorials are geared to be concise and provide step-by-step instructions with plenty of screen shots to walk you through the process visually. Each tutorial is available in C# and Visual Basic versions and includes a download of the complete code used. (This first tutorial is quite lengthy, but the rest are presented in much more digestible chunks.)

For these tutorials we'll be using a Microsoft SQL Server 2005 Express Edition version of the Northwind database placed in the App_Data directory. In addition to the database file, the App_Data folder also contains the SQL scripts for creating the database, in case you want to use a different database version. These scripts can be also bedownloaded directly from Microsoft, if you'd prefer. If you use a different SQL Server version of the Northwind database, you will need to update the NORTHWNDConnectionString setting in the application's Web.config file. The web application was built using Visual Studio 2005 Professional Edition as a file system-based Web site project. However, all of the tutorials will work equally well with the free version of Visual Studio 2005, Visual Web Developer.
In this tutorial we'll start from the very beginning and create the Data Access Layer (DAL), followed by creating the Business Logic Layer (BLL) in the second tutorial, and working on page layout and navigation in the third. The tutorials after the third one will build upon the foundation laid in the first three. We've got a lot to cover in this first tutorial, so fire up Visual Studio and let's get started!

Step 1: Creating a Web Project and Connecting to the Database

Before we can create our Data Access Layer (DAL), we first need to create a web site and setup our database. Start by creating a new file system-based ASP.NET web site. To accomplish this, go to the File menu and choose New Web Site, displaying the New Web Site dialog box. Choose the ASP.NET Web Site template, set the Location drop-down list to File System, choose a folder to place the web site, and set the language to C#.

Create a New File System-Based Web Site

Figure 1: Create a New File System-Based Web Site

This will create a new web site with a Default.aspx ASP.NET page and an App_Data folder.

With the web site created, the next step is to add a reference to the database in Visual Studio's Server Explorer. By adding a database to the Server Explorer you can add tables, stored procedures, views, and so on all from within Visual Studio. You can also view table data or create your own queries either by hand or graphically via the Query Builder. Furthermore, when we build the Typed DataSets for the DAL we'll need to point Visual Studio to the database from which the Typed DataSets should be constructed. While we can provide this connection information at that point in time, Visual Studio automatically populates a drop-down list of the databases already registered in the Server Explorer.

The steps for adding the Northwind database to the Server Explorer depend on whether you want to use the SQL Server 2005 Express Edition database in the App_Data folder or if you have a Microsoft SQL Server 2000 or 2005 database server setup that you want to use instead.

Using a Database in the App_Data Folder

If you do not have a SQL Server 2000 or 2005 database server to connect to, or you simply want to avoid having to add the database to a database server, you can use the SQL Server 2005 Express Edition version of the Northwind database that is located in the downloaded website's App_Data folder (NORTHWND.MDF).

A database placed in the App_Data folder is automatically added to the Server Explorer. Assuming you have SQL Server 2005 Express Edition installed on your machine you should see a node named NORTHWND.MDF in the Server Explorer, which you can expand and explore its tables, views, stored procedure, and so on (see Figure 2).

The App_Data folder can also hold Microsoft Access .mdb files, which, like their SQL Server counterparts, are automatically added to the Server Explorer. If you don't want to use any of the SQL Server options, you can alwaysdownload a Microsoft Access version of the Northwind database file and drop into the App_Data directory. Keep in mind, however, that Access databases aren't as feature-rich as SQL Server, and aren't designed to be used in web site scenarios. Furthermore, a couple of the 35+ tutorials will utilize certain database-level features that aren't supported by Access.

Connecting to the Database in a Microsoft SQL Server 2000 or 2005 Database Server

Alternatively, you may connect to a Northwind database installed on a database server. If the database server does not already have the Northwind database installed, you first must add it to database server by running the installation script included in this tutorial's download or by downloading the SQL Server 2000 version of Northwind and installation script directly from Microsoft's web site.

Once you have the database installed, go to the Server Explorer in Visual Studio, right-click on the Data Connections node, and choose Add Connection. If you don't see the Server Explorer go to the View / Server Explorer, or hit Ctrl+Alt+S. This will bring up the Add Connection dialog box, where you can specify the server to connect to, the authentication information, and the database name. Once you have successfully configured the database connection information and clicked the OK button, the database will be added as a node underneath the Data Connections node. You can expand the database node to explore its tables, views, stored procedures, and so on.

Add a Connection to Your Database Server's Northwind Database

Figure 2: Add a Connection to Your Database Server's Northwind Database

Step 2: Creating the Data Access Layer

When working with data one option is to embed the data-specific logic directly into the presentation layer (in a web application, the ASP.NET pages make up the presentation layer). This may take the form of writing ADO.NET code in the ASP.NET page's code portion or using the SqlDataSource control from the markup portion. In either case, this approach tightly couples the data access logic with the presentation layer. The recommended approach, however, is to separate the data access logic from the presentation layer. This separate layer is referred to as the Data Access Layer, DAL for short, and is typically implemented as a separate Class Library project. The benefits of this layered architecture are well documented (see the "Further Readings" section at the end of this tutorial for information on these advantages) and is the approach we will take in this series.

All code that is specific to the underlying data source such as creating a connection to the database, issuingSELECT, INSERT, UPDATE, and DELETE commands, and so on should be located in the DAL. The presentation layer should not contain any references to such data access code, but should instead make calls into the DAL for any and all data requests. Data Access Layers typically contain methods for accessing the underlying database data. The Northwind database, for example, has Products and Categories tables that record the products for sale and the categories to which they belong. In our DAL we will have methods like:

  • GetCategories(), which will return information about all of the categories
  • GetProducts(), which will return information about all of the products
  • GetProductsByCategoryID(categoryID), which will return all products that belong to a specified category
  • GetProductByProductID(productID), which will return information about a particular product

These methods, when invoked, will connect to the database, issue the appropriate query, and return the results. How we return these results is important. These methods could simply return a DataSet or DataReader populated by the database query, but ideally these results should be returned using strongly-typed objects. A strongly-typed object is one whose schema is rigidly defined at compile time, whereas the opposite, a loosely-typed object, is one whose schema is not known until runtime.

For example, the DataReader and the DataSet (by default) are loosely-typed objects since their schema is defined by the columns returned by the database query used to populate them. To access a particular column from a loosely-typed DataTable we need to use syntax like: DataTable.Rows[index]["columnName"]. The DataTable's loose typing in this example is exhibited by the fact that we need to access the column name using a string or ordinal index. A strongly-typed DataTable, on the other hand, will have each of its columns implemented as properties, resulting in code that looks like: DataTable.Rows[index].columnName.

To return strongly-typed objects, developers can either create their own custom business objects or use Typed DataSets. A business object is implemented by the developer as a class whose properties typically reflect the columns of the underlying database table the business object represents. A Typed DataSet is a class generated for you by Visual Studio based on a database schema and whose members are strongly-typed according to this schema. The Typed DataSet itself consists of classes that extend the ADO.NET DataSet, DataTable, and DataRow classes. In addition to strongly-typed DataTables, Typed DataSets now also include TableAdapters, which are classes with methods for populating the DataSet's DataTables and propagating modifications within the DataTables back to the database.

Note: For more information on the advantages and disadvantages of using Typed DataSets versus custom business objects, refer to Designing Data Tier Components and Passing Data Through Tiers.

We'll use strongly-typed DataSets for these tutorials' architecture. Figure 3 illustrates the workflow between the different layers of an application that uses Typed DataSets.

All Data Access Code is Relegated to the DAL

Figure 3: All Data Access Code is Relegated to the DAL

Creating a Typed DataSet and Table Adapter

To begin creating our DAL, we start by adding a Typed DataSet to our project. To accomplish this, right-click on the project node in the Solution Explorer and choose Add a New Item. Select the DataSet option from the list of templates and name it Northwind.xsd.

Choose to Add a New DataSet to Your Project

Figure 4: Choose to Add a New DataSet to Your Project

After clicking Add, when prompted to add the DataSet to the App_Code folder, choose Yes. The Designer for the Typed DataSet will then be displayed, and the TableAdapter Configuration Wizard will start, allowing you to add your first TableAdapter to the Typed DataSet.

A Typed DataSet serves as a strongly-typed collection of data; it is composed of strongly-typed DataTable instances, each of which is in turn composed of strongly-typed DataRow instances. We will create a strongly-typed DataTable for each of the underlying database tables that we need to work with in this tutorials series. Let's start with creating a DataTable for the Products table.

Keep in mind that strongly-typed DataTables do not include any information on how to access data from their underlying database table. In order to retrieve the data to populate the DataTable, we use a TableAdapter class, which functions as our Data Access Layer. For our Products DataTable, the TableAdapter will contain the methodsGetProducts(), GetProductByCategoryID(categoryID), and so on that we'll invoke from the presentation layer. The DataTable's role is to serve as the strongly-typed objects used to pass data between the layers.

The TableAdapter Configuration Wizard begins by prompting you to select which database to work with. The drop-down list shows those databases in the Server Explorer. If you did not add the Northwind database to the Server Explorer, you can click the New Connection button at this time to do so.

Choose the Northwind Database from the Drop-Down List

Figure 5: Choose the Northwind Database from the Drop-Down List

After selecting the database and clicking Next, you'll be asked if you want to save the connection string in theWeb.config file. By saving the connection string you'll avoid having it hard coded in the TableAdapter classes, which simplifies things if the connection string information changes in the future. If you opt to save the connection string in the configuration file it's placed in the <connectionStrings> section, which can be optionally encrypted for improved security or modified later through the new ASP.NET 2.0 Property Page within the IIS GUI Admin Tool, which is more ideal for administrators.

Save the Connection String to Web.config

Figure 6: Save the Connection String to Web.config

Next, we need to define the schema for the first strongly-typed DataTable and provide the first method for our TableAdapter to use when populating the strongly-typed DataSet. These two steps are accomplished simultaneously by creating a query that returns the columns from the table that we want reflected in our DataTable. At the end of the wizard we'll give a method name to this query. Once that's been accomplished, this method can be invoked from our presentation layer. The method will execute the defined query and populate a strongly-typed DataTable.

To get started defining the SQL query we must first indicate how we want the TableAdapter to issue the query. We can use an ad-hoc SQL statement, create a new stored procedure, or use an existing stored procedure. For these tutorials we'll use ad-hoc SQL statements. Refer to Brian Noyes's article, Build a Data Access Layer with the Visual Studio 2005 DataSet Designer for an example of using stored procedures.

Query the Data Using an Ad-Hoc SQL Statement

Figure 7: Query the Data Using an Ad-Hoc SQL Statement

At this point we can type in the SQL query by hand. When creating the first method in the TableAdapter you typically want to have the query return those columns that need to be expressed in the corresponding DataTable. We can accomplish this by creating a query that returns all columns and all rows from the Products table:

Enter the SQL Query Into the Textbox

Figure 8: Enter the SQL Query Into the Textbox

Alternatively, use the Query Builder and graphically construct the query, as shown in Figure 9.

Create the Query Graphically, through the Query Editor

Figure 9: Create the Query Graphically, through the Query Editor

After creating the query, but before moving onto the next screen, click the Advanced Options button. In Web Site Projects, "Generate Insert, Update, and Delete statements" is the only advanced option selected by default; if you run this wizard from a Class Library or a Windows Project the "Use optimistic concurrency" option will also be selected. Leave the "Use optimistic concurrency" option unchecked for now. We'll examine optimistic concurrency in future tutorials.

Select Only the  Generate Insert, Update, and Delete statements  Option

Figure 10: Select Only the Generate Insert, Update, and Delete statements Option

After verifying the advanced options, click Next to proceed to the final screen. Here we are asked to select which methods to add to the TableAdapter. There are two patterns for populating data:

  • Fill a DataTable with this approach a method is created that takes in a DataTable as a parameter and populates it based on the results of the query. The ADO.NET DataAdapter class, for example, implements this pattern with its Fill() method.
  • Return a DataTable with this approach the method creates and fills the DataTable for you and returns it as the methods return value.

You can have the TableAdapter implement one or both of these patterns. You can also rename the methods provided here. Let's leave both checkboxes checked, even though we'll only be using the latter pattern throughout these tutorials. Also, let's rename the rather generic GetData method to GetProducts.

If checked, the final checkbox, "GenerateDBDirectMethods," creates Insert(), Update(), and Delete() methods for the TableAdapter. If you leave this option unchecked, all updates will need to be done through the TableAdapter's sole Update() method, which takes in the Typed DataSet, a DataTable, a single DataRow, or an array of DataRows. (If you've unchecked the "Generate Insert, Update, and Delete statements" option from the advanced properties in Figure 9 this checkbox's setting will have no effect.) Let's leave this checkbox selected.

Change the Method Name from GetData to GetProducts

Figure 11: Change the Method Name from GetData to GetProducts

Complete the wizard by clicking Finish. After the wizard closes we are returned to the DataSet Designer which shows the DataTable we just created. You can see the list of columns in the Products DataTable (ProductID,ProductName, and so on), as well as the methods of the ProductsTableAdapter (Fill() and GetProducts()).

The Products DataTable and ProductsTableAdapter have been Added to the Typed DataSet

Figure 12: The Products DataTable and ProductsTableAdapter have been Added to the Typed DataSet

At this point we have a Typed DataSet with a single DataTable (Northwind.Products) and a strongly-typed DataAdapter class (NorthwindTableAdapters.ProductsTableAdapter) with a GetProducts() method. These objects can be used to access a list of all products from code like:

NorthwindTableAdapters.ProductsTableAdapter productsAdapter =
new NorthwindTableAdapters.ProductsTableAdapter();
Northwind.ProductsDataTable products;
products = productsAdapter.GetProducts();
foreach (Northwind.ProductsRow productRow in products)
Response.Write("Product: " + productRow.ProductName + "<br />");

This code did not require us to write one bit of data access-specific code. We did not have to instantiate any ADO.NET classes, we didn't have to refer to any connection strings, SQL queries, or stored procedures. Instead, the TableAdapter provides the low-level data access code for us.

Each object used in this example is also strongly-typed, allowing Visual Studio to provide IntelliSense and compile-time type checking. And best of all the DataTables returned by the TableAdapter can be bound to ASP.NET data Web controls, such as the GridView, DetailsView, DropDownList, CheckBoxList, and several others. The following example illustrates binding the DataTable returned by the GetProducts() method to a GridView in just a scant three lines of code within the Page_Load event handler.

AllProducts.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="AllProducts.aspx.cs"
Inherits="AllProducts" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>View All Products in a GridView</title>
<link href="Styles.css" rel="stylesheet" type="text/css" />
</head>
<body>
<form id="form1" runat="server">
<div>
<h2>
All Products</h2>
<p>
<asp:GridView ID="GridView1" runat="server"
CssClass="DataWebControlStyle">
<HeaderStyle CssClass="HeaderStyle" />
<AlternatingRowStyle CssClass="AlternatingRowStyle" />
</asp:GridView>
</p>
</div>
</form>
</body>
</html>

AllProducts.aspx.cs

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using NorthwindTableAdapters;
public partial class AllProducts : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
ProductsTableAdapter productsAdapter = new
ProductsTableAdapter();
GridView1.DataSource = productsAdapter.GetProducts();
GridView1.DataBind();
}
}

The List of Products is Displayed in a GridView

Figure 13: The List of Products is Displayed in a GridView

While this example required that we write three lines of code in our ASP.NET page's Page_Load event handler, in future tutorials we'll examine how to use the ObjectDataSource to declaratively retrieve the data from the DAL. With the ObjectDataSource we'll not have to write any code and will get paging and sorting support as well!

Step 3: Adding Parameterized Methods to the Data Access Layer

At this point our ProductsTableAdapter class has but one method, GetProducts(), which returns all of the products in the database. While being able to work with all products is definitely useful, there are times when we'll want to retrieve information about a specific product, or all products that belong to a particular category. To add such functionality to our Data Access Layer we can add parameterized methods to the TableAdapter.

Let's add the GetProductsByCategoryID(categoryID) method. To add a new method to the DAL, return to the DataSet Designer, right-click in the ProductsTableAdapter section, and choose Add Query.

Right-Click on the TableAdapter and Choose Add Query

Figure 14: Right-Click on the TableAdapter and Choose Add Query

We are first prompted about whether we want to access the database using an ad-hoc SQL statement or a new or existing stored procedure. Let's choose to use an ad-hoc SQL statement again. Next, we are asked what type of SQL query we'd like to use. Since we want to return all products that belong to a specified category, we want to write a SELECT statement which returns rows.

Choose to Create a SELECT Statement Which Returns Rows

Figure 15: Choose to Create a SELECT Statement Which Returns Rows

The next step is to define the SQL query used to access the data. Since we want to return only those products that belong to a particular category, I use the same SELECT statement from GetProducts(), but add the followingWHERE clause: WHERE CategoryID = @CategoryID. The @CategoryID parameter indicates to the TableAdapter wizard that the method we're creating will require an input parameter of the corresponding type (namely, a nullable integer).

Enter a Query to Only Return Products in a Specified Category

Figure 16: Enter a Query to Only Return Products in a Specified Category

In the final step we can choose which data access patterns to use, as well as customize the names of the methods generated. For the Fill pattern, let's change the name to FillByCategoryID and for the return a DataTable return pattern (the GetX methods), let's use GetProductsByCategoryID.

Choose the Names for the TableAdapter Methods

Figure 17: Choose the Names for the TableAdapter Methods

After completing the wizard, the DataSet Designer includes the new TableAdapter methods.

The Products Can Now be Queried by Category

Figure 18: The Products Can Now be Queried by Category

Take a moment to add a GetProductByProductID(productID) method using the same technique.

These parameterized queries can be tested directly from the DataSet Designer. Right-click on the method in the TableAdapter and choose Preview Data. Next, enter the values to use for the parameters and click Preview.

Those Products Belonging to the Beverages Category are Shown

Figure 19: Those Products Belonging to the Beverages Category are Shown

With the GetProductsByCategoryID(categoryID) method in our DAL, we can now create an ASP.NET page that displays only those products in a specified category. The following example shows all products that are in the Beverages category, which have a CategoryID of 1.

Beverages.asp

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Beverages.aspx.cs"
Inherits="Beverages" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitled Page</title>
<link href="Styles.css" rel="stylesheet" type="text/css" />
</head>
<body>
<form id="form1" runat="server">
<div>
<h2>Beverages</h2>
<p>
<asp:GridView ID="GridView1" runat="server"
CssClass="DataWebControlStyle">
<HeaderStyle CssClass="HeaderStyle" />
<AlternatingRowStyle CssClass="AlternatingRowStyle" />
</asp:GridView>
</p>
</div>
</form>
</body>
</html>

Beverages.aspx.cs

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using NorthwindTableAdapters;
public partial class Beverages : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
ProductsTableAdapter productsAdapter = new
ProductsTableAdapter();
GridView1.DataSource =
productsAdapter.GetProductsByCategoryID(1);
GridView1.DataBind();
}
}

Those Products in the Beverages Category are Displayed

Figure 20: Those Products in the Beverages Category are Displayed

Step 4: Inserting, Updating, and Deleting Data

There are two patterns commonly used for inserting, updating, and deleting data. The first pattern, which I'll call the database direct pattern, involves creating methods that, when invoked, issue an INSERT, UPDATE, or DELETEcommand to the database that operates on a single database record. Such methods are typically passed in a series of scalar values (integers, strings, Booleans, DateTimes, and so on) that correspond to the values to insert, update, or delete. For example, with this pattern for the Products table the delete method would take in an integer parameter, indicating the ProductID of the record to delete, while the insert method would take in a string for theProductName, a decimal for the UnitPrice, an integer for the UnitsOnStock, and so on.

Each Insert, Update, and Delete Request is Sent to the Database Immediately

Figure 21: Each Insert, Update, and Delete Request is Sent to the Database Immediately

The other pattern, which I'll refer to as the batch update pattern, is to update an entire DataSet, DataTable, or collection of DataRows in one method call. With this pattern a developer deletes, inserts, and modifies the DataRows in a DataTable and then passes those DataRows or DataTable into an update method. This method then enumerates the DataRows passed in, determines whether or not they've been modified, added, or deleted (via the DataRow's RowState property value), and issues the appropriate database request for each record.

All Changes are Synchronized with the Database When the Update Method is Invoked

Figure 22: All Changes are Synchronized with the Database When the Update Method is Invoked

The TableAdapter uses the batch update pattern by default, but also supports the DB direct pattern. Since we selected the "Generate Insert, Update, and Delete statements" option from the Advanced Properties when creating our TableAdapter, the ProductsTableAdapter contains an Update() method, which implements the batch update pattern. Specifically, the TableAdapter contains an Update() method that can be passed the Typed DataSet, a strongly-typed DataTable, or one or more DataRows. If you left the "GenerateDBDirectMethods" checkbox checked when first creating the TableAdapter the DB direct pattern will also be implemented via Insert(), Update(), andDelete() methods.

Both data modification patterns use the TableAdapter's InsertCommand, UpdateCommand, and DeleteCommandproperties to issue their INSERT, UPDATE, and DELETE commands to the database. You can inspect and modify the InsertCommand, UpdateCommand, and DeleteCommand properties by clicking on the TableAdapter in the DataSet Designer and then going to the Properties window. (Make sure you have selected the TableAdapter, and that the ProductsTableAdapter object is the one selected in the drop-down list in the Properties window.)

The TableAdapter has InsertCommand, UpdateCommand, and DeleteCommand Properties

Figure 23: The TableAdapter has InsertCommand, UpdateCommand, and DeleteCommand Properties

To examine or modify any of these database command properties, click on the CommandText subproperty, which will bring up the Query Builder.

Configure the INSERT, UPDATE, and DELETE Statements in the Query Builder

Figure 24: Configure the INSERT, UPDATE, and DELETE Statements in the Query Builder

The following code example shows how to use the batch update pattern to double the price of all products that are not discontinued and that have 25 units in stock or less:

NorthwindTableAdapters.ProductsTableAdapter productsAdapter =
new NorthwindTableAdapters.ProductsTableAdapter();
// For each product, double its price if it is not discontinued and
// there are 25 items in stock or less
Northwind.ProductsDataTable products = productsAdapter.GetProducts();
foreach (Northwind.ProductsRow product in products)
if (!product.Discontinued && product.UnitsInStock <= 25)
product.UnitPrice *= 2;
// Update the products
productsAdapter.Update(products);

The code below illustrates how to use the DB direct pattern to programmatically delete a particular product, then update one, and then add a new one:

NorthwindTableAdapters.ProductsTableAdapter productsAdapter =
new NorthwindTableAdapters.ProductsTableAdapter();
// Delete the product with ProductID 3
productsAdapter.Delete(3);
// Update Chai (ProductID of 1), setting the UnitsOnOrder to 15
productsAdapter.Update("Chai", 1, 1, "10 boxes x 20 bags",
18.0m, 39, 15, 10, false, 1);
// Add a new product
productsAdapter.Insert("New Product", 1, 1,
"12 tins per carton", 14.95m, 15, 0, 10, false);

Creating Custom Insert, Update, and Delete Methods

The Insert(), Update(), and Delete() methods created by the DB direct method can be a bit cumbersome, especially for tables with many columns. Looking at the previous code example, without IntelliSense's help it's not particularly clear what Products table column maps to each input parameter to the Update() and Insert() methods. There may be times when we only want to update a single column or two, or want a customized Insert() method that will, perhaps, return the value of the newly inserted record's IDENTITY (auto-increment) field.

To create such a custom method, return to the DataSet Designer. Right-click on the TableAdapter and choose Add Query, returning to the TableAdapter wizard. On the second screen we can indicate the type of query to create. Let's create a method that adds a new product and then returns the value of the newly added record's ProductID. Therefore, opt to create an INSERT query.

Create a Method to Add a New Row to the Products Table

Figure 25: Create a Method to Add a New Row to the Products Table

On the next screen the InsertCommand's CommandText appears. Augment this query by adding SELECT SCOPE_IDENTITY() at the end of the query, which will return the last identity value inserted into an IDENTITYcolumn in the same scope. (See the technical documentation for more information about SCOPE_IDENTITY() and why you probably want to use SCOPE_IDENTITY() in lieu of @@IDENTITY.) Make sure that you end the INSERTstatement with a semi-colon before adding the SELECT statement.

Augment the Query to Return the SCOPE_IDENTITY() Value

Figure 26: Augment the Query to Return the SCOPE_IDENTITY() Value

Finally, name the new method InsertProduct.

Set the New Method Name to InsertProduct

Figure 27: Set the New Method Name to InsertProduct

When you return to the DataSet Designer you'll see that the ProductsTableAdapter contains a new method,InsertProduct. If this new method doesn't have a parameter for each column in the Products table, chances are you forgot to terminate the INSERT statement with a semi-colon. Configure the InsertProduct method and ensure you have a semi-colon delimiting the INSERT and SELECT statements.

By default, insert methods issue non-query methods, meaning that they return the number of affected rows. However, we want the InsertProduct method to return the value returned by the query, not the number of rows affected. To accomplish this, adjust the InsertProduct method's ExecuteMode property to Scalar.

Change the ExecuteMode Property to Scalar

Figure 28: Change the ExecuteMode Property to Scalar

The following code shows this new InsertProduct method in action:

NorthwindTableAdapters.ProductsTableAdapter productsAdapter =
new NorthwindTableAdapters.ProductsTableAdapter();
// Add a new product
int new_productID = Convert.ToInt32(productsAdapter.InsertProduct
("New Product", 1, 1, "12 tins per carton", 14.95m, 10, 0, 10, false));
// On second thought, delete the product
productsAdapter.Delete(new_productID);

Step 5: Completing the Data Access Layer

Note that the ProductsTableAdapters class returns the CategoryID and SupplierID values from the Productstable, but doesn't include the CategoryName column from the Categories table or the CompanyName column from the Suppliers table, although these are likely the columns we want to display when showing product information. We can augment the TableAdapter's initial method, GetProducts(), to include both the CategoryNameand CompanyName column values, which will update the strongly-typed DataTable to include these new columns as well.

This can present a problem, however, as the TableAdapter's methods for inserting, updating, and deleting data are based off of this initial method. Fortunately, the auto-generated methods for inserting, updating, and deleting are not affected by subqueries in the SELECT clause. By taking care to add our queries to Categories and Suppliers as subqueries, rather than JOINs, we'll avoid having to rework those methods for modifying data. Right-click on theGetProducts() method in the ProductsTableAdapter and choose Configure. Then, adjust the SELECT clause so that it looks like:

SELECT ProductID, ProductName, SupplierID, CategoryID,
QuantityPerUnit, UnitPrice, UnitsInStock, UnitsOnOrder, ReorderLevel, Discontinued,
(SELECT CategoryName FROM Categories
WHERE Categories.CategoryID = Products.CategoryID) as CategoryName,
(SELECT CompanyName FROM Suppliers
WHERE Suppliers.SupplierID = Products.SupplierID) as SupplierName
FROM Products

Update the SELECT Statement for the GetProducts() Method

Figure 29: Update the SELECT Statement for the GetProducts() Method

After updating the GetProducts() method to use this new query the DataTable will include two new columns:CategoryName and SupplierName.

The Products DataTable has Two New Columns

Figure 30: The Products DataTable has Two New Columns

Take a moment to update the SELECT clause in the GetProductsByCategoryID(categoryID) method as well.

If you update the GetProducts() SELECT using JOIN syntax the DataSet Designer won't be able to auto-generate the methods for inserting, updating, and deleting database data using the DB direct pattern. Instead, you'll have to manually create them much like we did with the InsertProduct method earlier in this tutorial. Furthermore, you'll manually have to provide the InsertCommand, UpdateCommand, and DeleteCommand property values if you want to use the batch updating pattern.

Adding the Remaining TableAdapters

Up until now, we've only looked at working with a single TableAdapter for a single database table. However, the Northwind database contains several related tables that we'll need to work with in our web application. A Typed DataSet can contain multiple, related DataTables. Therefore, to complete our DAL we need to add DataTables for the other tables we'll be using in these tutorials. To add a new TableAdapter to a Typed DataSet, open the DataSet Designer, right-click in the Designer, and choose Add / TableAdapter. This will create a new DataTable and TableAdapter and walk you through the wizard we examined earlier in this tutorial.

Take a few minutes to create the following TableAdapters and methods using the following queries. Note that the queries in the ProductsTableAdapter include the subqueries to grab each product's category and supplier names. Additionally, if you've been following along, you've already added the ProductsTableAdapter class'sGetProducts() and GetProductsByCategoryID(categoryID) methods.

  • ProductsTableAdapter
    • GetProducts:
      SELECT ProductID, ProductName, SupplierID,
      CategoryID, QuantityPerUnit, UnitPrice, UnitsInStock,
      UnitsOnOrder, ReorderLevel, Discontinued
      ,
      (SELECT CategoryName FROM Categories WHERE
      Categories.CategoryID = Products.CategoryID) as
      CategoryName, (SELECT CompanyName FROM Suppliers
      WHERE Suppliers.SupplierID = Products.SupplierID)
      as SupplierName
      FROM Products
    • GetProductsByCategoryID:
      SELECT ProductID, ProductName, SupplierID, CategoryID,
      QuantityPerUnit, UnitPrice, UnitsInStock, UnitsOnOrder,
      ReorderLevel, Discontinued
      , (SELECT CategoryName
      FROM Categories WHERE Categories.CategoryID =
      Products.CategoryID) as CategoryName,
      (SELECT CompanyName FROM Suppliers WHERE
      Suppliers.SupplierID = Products.SupplierID)
      as SupplierName
      FROM Products
      WHERE CategoryID = @CategoryID
    • GetProductsBySupplierID:
      SELECT ProductID, ProductName, SupplierID, CategoryID,
      QuantityPerUnit, UnitPrice, UnitsInStock, UnitsOnOrder,
      ReorderLevel, Discontinued
      , (SELECT CategoryName
      FROM Categories WHERE Categories.CategoryID =
      Products.CategoryID) as CategoryName,
      (SELECT CompanyName FROM Suppliers WHERE
      Suppliers.SupplierID = Products.SupplierID) as SupplierName
      FROM Products
      WHERE SupplierID = @SupplierID
    • GetProductByProductID:
      SELECT ProductID, ProductName, SupplierID, CategoryID,
      QuantityPerUnit, UnitPrice, UnitsInStock, UnitsOnOrder,
      ReorderLevel, Discontinued
      , (SELECT CategoryName
      FROM Categories WHERE Categories.CategoryID =
      Products.CategoryID) as CategoryName,
      (SELECT CompanyName FROM Suppliers WHERE Suppliers.SupplierID = Products.SupplierID)
      as SupplierName
      FROM Products
      WHERE ProductID = @ProductID
  • CategoriesTableAdapter
    • GetCategories:
      SELECT CategoryID, CategoryName, Description
      FROM Categories
    • GetCategoryByCategoryID:
      SELECT CategoryID, CategoryName, Description
      FROM Categories
      WHERE CategoryID = @CategoryID
  • SuppliersTableAdapter
    • GetSuppliers:
      SELECT SupplierID, CompanyName, Address,
      City, Country, Phone
      FROM Suppliers
    • GetSuppliersByCountry:
      SELECT SupplierID, CompanyName, Address,
      City, Country, Phone
      FROM Suppliers
      WHERE Country = @Country
    • GetSupplierBySupplierID:
      SELECT SupplierID, CompanyName, Address,
      City, Country, Phone
      FROM Suppliers
      WHERE SupplierID = @SupplierID
  • EmployeesTableAdapter
    • GetEmployees:
      SELECT EmployeeID, LastName, FirstName, Title,
      HireDate, ReportsTo, Country
      FROM Employees
    • GetEmployeesByManager:
      SELECT EmployeeID, LastName, FirstName, Title,
      HireDate, ReportsTo, Country
      FROM Employees
      WHERE ReportsTo = @ManagerID
    • GetEmployeeByEmployeeID:
      SELECT EmployeeID, LastName, FirstName, Title,
      HireDate, ReportsTo, Country
      FROM Employees
      WHERE EmployeeID = @EmployeeID

The DataSet Designer After the Four TableAdapters Have Been Added

Figure 31: The DataSet Designer After the Four TableAdapters Have Been Added

Adding Custom Code to the DAL

The TableAdapters and DataTables added to the Typed DataSet are expressed as an XML Schema Definition file (Northwind.xsd). You can view this schema information by right-clicking on the Northwind.xsd file in the Solution Explorer and choosing View Code.

The XML Schema Definition (XSD) File for the Northwinds Typed DataSet

Figure 32: The XML Schema Definition (XSD) File for the Northwinds Typed DataSet

This schema information is translated into C# or Visual Basic code at design time when compiled or at runtime (if needed), at which point you can step through it with the debugger. To view this auto-generated code go to the Class View and drill down to the TableAdapter or Typed DataSet classes. If you don't see the Class View on your screen, go to the View menu and select it from there, or hit Ctrl+Shift+C. From the Class View you can see the properties, methods, and events of the Typed DataSet and TableAdapter classes. To view the code for a particular method, double-click the method name in the Class View or right-click on it and choose Go To Definition.

Inspect the Auto-Generated Code by Selecting Go To Definition from the Class View

Figure 33: Inspect the Auto-Generated Code by Selecting Go To Definition from the Class View

While auto-generated code can be a great time saver, the code is often very generic and needs to be customized to meet the unique needs of an application. The risk of extending auto-generated code, though, is that the tool that generated the code might decide it's time to "regenerate" and overwrite your customizations. With .NET 2.0's new partial class concept, it's easy to split a class across multiple files. This enables us to add our own methods, properties, and events to the auto-generated classes without having to worry about Visual Studio overwriting our customizations.

To demonstrate how to customize the DAL, let's add a GetProducts() method to the SuppliersRow class. TheSuppliersRow class represents a single record in the Suppliers table; each supplier can provider zero to many products, so GetProducts() will return those products of the specified supplier. To accomplish this create a new class file in the App_Code folder named SuppliersRow.cs and add the following code:

using System;
using System.Data;
using NorthwindTableAdapters;
public partial class Northwind
{
public partial class SuppliersRow
{
public Northwind.ProductsDataTable GetProducts()
{
ProductsTableAdapter productsAdapter =
new ProductsTableAdapter();
return
productsAdapter.GetProductsBySupplierID(this.SupplierID);
}
}
}

This partial class instructs the compiler that when building the Northwind.SuppliersRow class to include theGetProducts() method we just defined. If you build your project and then return to the Class View you'll seeGetProducts() now listed as a method of Northwind.SuppliersRow.

The GetProducts() Method is Now Part of the Northwind.SuppliersRow Class

Figure 34: The GetProducts() Method is Now Part of the Northwind.SuppliersRow Class

The GetProducts() method can now be used to enumerate the set of products for a particular supplier, as the following code shows:

NorthwindTableAdapters.SuppliersTableAdapter suppliersAdapter =
new NorthwindTableAdapters.SuppliersTableAdapter();
// Get all of the suppliers
Northwind.SuppliersDataTable suppliers =
suppliersAdapter.GetSuppliers();
// Enumerate the suppliers
foreach (Northwind.SuppliersRow supplier in suppliers)
{
Response.Write("Supplier: " + supplier.CompanyName);
Response.Write("<ul>");
// List the products for this supplier
Northwind.ProductsDataTable products = supplier.GetProducts();
foreach (Northwind.ProductsRow product in products)
Response.Write("<li>" + product.ProductName + "</li>");
Response.Write("</ul><p> </p>");
}

This data can also be displayed in any of ASP.NET's data Web controls. The following page uses a GridView control with two fields:

  • A BoundField that displays the name of each supplier, and
  • A TemplateField that contains a BulletedList control that is bound to the results returned by the GetProducts()method for each supplier.

We'll examine how to display such master-detail reports in future tutorials. For now, this example is designed to illustrate using the custom method added to the Northwind.SuppliersRow class.

SuppliersAndProducts.aspx

<%@ Page Language="C#" CodeFile="SuppliersAndProducts.aspx.cs"
AutoEventWireup="true" Inherits="SuppliersAndProducts" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitled Page</title>
<link href="Styles.css" rel="stylesheet" type="text/css" />
</head>
<body>
<form id="form1" runat="server">
<div>
<h2>
Suppliers and Their Products</h2>
<p>
<asp:GridView ID="GridView1" runat="server"
AutoGenerateColumns="False"
CssClass="DataWebControlStyle">
<HeaderStyle CssClass="HeaderStyle" />
<AlternatingRowStyle CssClass="AlternatingRowStyle" />
<Columns>
<asp:BoundField DataField="CompanyName"
HeaderText="Supplier" />
<asp:TemplateField HeaderText="Products">
<ItemTemplate>
<asp:BulletedList ID="BulletedList1"
runat="server" DataSource="<%# ((Northwind.SuppliersRow) ((System.Data.DataRowView) Container.DataItem).Row).GetProducts() %>"
DataTextField="ProductName">
</asp:BulletedList>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
</p>
</div>
</form>
</body>
</html>

SuppliersAndProducts.aspx.cs

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using NorthwindTableAdapters;
public partial class SuppliersAndProducts : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
SuppliersTableAdapter suppliersAdapter = new
SuppliersTableAdapter();
GridView1.DataSource = suppliersAdapter.GetSuppliers();
GridView1.DataBind();
}
}

The Supplier's Company Name is Listed in the Left Column, Their Products in the Right

Figure 35: The Supplier's Company Name is Listed in the Left Column, Their Products in the Right

WCF Architecture

The following figure illustrates the major components of WCF.

Figure 1: WCF Architecture

Contracts

Contracts layer are next to that of Application layer. Developer will directly use this contract to develop the service. We are also going to do the same now. Let us see briefly what these contracts will do for us and we will also know that WCF is working on message system.

Service contracts

- Describe about the operation that service can provide. Example, Service provided to know the temperature of the city based on the zip code, this service we call as Service contract. It will be created using Service and Operational Contract attribute.

Data contract

- It describes the custom data type which is exposed to the client. This defines the data types, are passed to and from service. Data types like int, string are identified by the client because it is already mention in XML schema definition language document, but custom created class or datatype cannot be identified by the client e.g. Employee data type. By using DataContract we can make client aware that we are using Employee data type for returning or passing parameter to the method.

Message Contract

- Default SOAP message format is provided by the WCF runtime for communication between Client and service. If it is not meeting your requirements then we can create our own message format. This can be achieved by using Message Contract attribute.

Policies and Binding

- Specify conditions required to communicate with a service e.g security requirement to communicate with service, protocol and encoding used for binding.

Service Runtime

- It contains the behaviors that occur during runtime of service.

  • Throttling Behavior- Controls how many messages are processed.
  • Error Behavior - Specifies what occurs, when internal error occurs on the service.
  • Metadata Behavior - Tells how and whether metadata is available to outside world.
  • Instance Behavior - Specifies how many instance of the service has to be created while running.
  • Transaction Behavior - Enables the rollback of transacted operations if a failure occurs.
  • Dispatch Behavior - Controls how a message is processed by the WCF Infrastructure.

Messaging

- Messaging layer is composed of channels. A channel is a component that processes a message in some way, for example, by authenticating a message. A set of channels is also known as a channel stack. Channels are the core abstraction for sending message to and receiving message from an Endpoint. Broadly we can categories channels as

  • Transport Channels

    Handles sending and receiving message from network. Protocols like HTTP, TCP, name pipes and MSMQ.

  • Protocol Channels

    Implements SOAP based protocol by processing and possibly modifying message. E.g. WS-Security and WS-Reliability.

Activation and Hosting

- Services can be hosted or executed, so that it will be available to everyone accessing from the client. WCF service can be hosted by following mechanism

  • IIS

    Internet information Service provides number of advantages if a Service uses Http as protocol. It does not require Host code to activate the service, it automatically activates service code.

  • Windows Activation Service

    (WAS) is the new process activation mechanism that ships with IIS 7.0. In addition to HTTP based communication, WCF can also use WAS to provide message-based activation over other protocols, such as TCP and named pipes.

  • Self-Hosting

    WCF service can be self hosted as console application, Win Forms or WPF application with graphical UI.

  • Windows Service

    WCF can also be hosted as a Windows Service, so that it is under control of the Service Control Manager (SCM).

Connection String Encryption in Web.config using C#

Almost all ASP.NET web sites connect database and one of the best practices in ASP.NET is to store your database connection string outside your source code typically in web configuration file (web.config). This gives you benefit of changing your database related information such as the server name, user id or password without any modification or compilation of your source code. To provide additional security of important connection string information you should always encrypt your connection string in web.config file.

ASP.NET 2.0 allow you to encrypt and decrypt your connection string in web.config. In the following tutorial, I will show you how you can encrypt and decrypt connection strings in C# using .NET Framework built in classes available in System.Configuration and System.Web.Configuration namespaces.

To test the following code you should have your connection string in web.config file as following code shows:

<configuration>
<connectionStrings>
<add name="MyConnectionString"
connectionString="Server=TestServer; Database=TestDB; UID=test; PWD=test"
providerName="System.Data.SqlClient" />
</connectionStrings>
</configuration>

Here is the C# code to encrypt and decrypt connection string. Make sure you have reference of System.Configuration and System.Web.Configuration available to test this code.
Encryption

try
{
Configuration config = WebConfigurationManager.OpenWebConfiguration("~");
ConfigurationSection section = config.GetSection("connectionStrings");
if (!section.SectionInformation.IsProtected)
{
section.SectionInformation.ProtectSection("RSAProtectedConfigurationProvider");
config.Save();
}
}
catch (Exception ex)
{ }

Decryption

try
{
Configuration config = WebConfigurationManager.OpenWebConfiguration("~");
ConfigurationSection section = config.GetSection("connectionStrings");
if (section.SectionInformation.IsProtected)
{
section.SectionInformation.UnprotectSection();
config.Save();
}
}
catch (Exception ex)
{ }

Download Source Code Download Source Code

Display Photos in ASP.NET using Flickr.NET API

One of the most common ingredients of any successful website is to display photos to the site visitors along with photos and their metadata search facility. There are number of photo sharing web sites and services providing the large number of photos for websites and blogs. The most popular and commonly used site is Flickr.com, which provides very flexible and powerful API to web developers and exposes almost all the data stored on the site to offer web developers limitless possibilities for creating mashups, widgets, etc. Due to the popularity of Flickr API, many client libraries are available for almost all programming languages such as .NET, Java or PHP. These libraries make development with Flickr API even easier by hiding lower level API details and also allows you to work with your favorite programming language and environment. In this tutorial, I will show you how you can use one such library Flickr.NET to search and display photos using C# and ASP.NET.
Using Flickr.NET API in ASP.NET
Before I start this tutorial, please keep in mind that the developer key and shared secret is required to make requests to the Flickr API so make sure you have got your developer key and shared secret from the Flckr website at the following URL.
http://www.flickr.com/services/api
You also make sure that you have downloaded the latest version of Flickr.NET API from codeplex website.
http://flickrnet.codeplex.com
To get started, create a new ASP.NET website in Visual Studio and add the reference of FlickrNet.dll you just downloaded from codeplex. To create an interface shown in the above figure, you need to add a table with three rows and two columns. Inside that table, you need to add search textbox, go button, some labels and a DataList control to show thumbnails. Following is the complete markup of the page used in this tutorial.
<div style="text-align: center">
<center>
<table cellpadding="5" cellspacing="0" style="border: 2px solid #0066CC; width: 60%;">
<tr>
<td style="width: 40%;">
Search:
<asp:TextBox ID="SearchTextBox" runat="server"></asp:TextBox>
<asp:Button ID="GoButton" runat="server" Text="GO"
OnClick="GoButton_Click" />
</td>
<td style="vertical-align: top">
<asp:Label ID="PhotoDateTaken" runat="server"></asp:Label>
</td>
</tr>
<tr>
<td style="vertical-align: top">
<asp:DataList ID="ThumbnailsList" runat="server" HorizontalAlign="Center"
RepeatColumns="3" Width="100%"
OnSelectedIndexChanged="ThumbnailsList_SelectedIndexChanged">
<ItemStyle HorizontalAlign="Center" />
<ItemTemplate>
<asp:ImageButton ID="ThumbnailImage" runat="server"
ImageUrl='<%# Eval("SquareThumbnailUrl") %>'
AlternateText='<%# Eval("Title") %>'
ToolTip='<%# Eval("Title") %>
'
CommandName="Select">
</asp:ImageButton>
<asp:Literal ID="HiddenPhotoId" runat="server"
Text='<%# Eval("PhotoId") %>' Visible="false" />
<asp:Literal ID="HiddenPhotoUrl" runat="server"
Text='<%# Eval("MediumUrl") %>' Visible="false" />
</ItemTemplate>
</asp:DataList>
</td>
<td style="vertical-align: top">
<asp:Image ID="PreviewImage" runat="server" />
</td>
</tr>
<tr>
<td style="vertical-align: top">&nbsp;</td>
<td style="vertical-align: top">
<asp:Label ID="PhotoDescription" runat="server"></asp:Label>
</td>
</tr>
</table>
</center>
</div>
The DataList control used in the above markup is using an ImageButton control to display image thumbnails inside the ItemTemplate. Notice how the ImageUrl property of the ImageButton is bound with SquareThumbnailUrl property of the Flickr.NET API Photo class. Furthermore, notice the AlternateText and ToolTip properties are bound with Title property. I also used two hidden literal controls to store PhotoId and itsMediumUrl properties, which will be used to display photo preview and to get more details like its description or date the photo is taken from Flickr website.
It is now time to show you the Flickr.NET API in action by moving to the page code behind file. Declare the following two variables on top of the class and store your developer key and shared secret in them.
string flickrKey = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";
string sharedSecret = "xxxxxxxxxxxxxxx";
Define the following GetPhotos method to search photos from Flickr website using Flickr.NET API and to bind the DataList with the photos returned from Flickr. This method will be called in Page Load event with default keyword and then from Go button click with the keyword user will specify in the search textbox.
private void GetPhotos(string tag)
{
PhotoSearchOptions options = new PhotoSearchOptions();
options.PerPage = 12;
options.Page = 1;
options.SortOrder = PhotoSearchSortOrder.DatePostedDescending;
options.MediaType = MediaType.Photos;
options.Extras = PhotoSearchExtras.All;
options.Tags = tag;
Flickr flickr = new Flickr(flickrKey, sharedSecret);
PhotoCollection photos = flickr.PhotosSearch(options);

ThumbnailsList.DataSource = photos;
ThumbnailsList.DataBind();
}
The method GetPhotos first declares an object of PhotoSearchOptions class that allows us to set all the search related parameters in a single place. You can set how many photos you want to retrieve per page along with the current page index. You can set the sort order, media type (photos, videos etc.) to fetch from Flickr website. You need to set the Tags property with any string value you want to search. Flickr.NET API also exposes Flickr class that have PhotoSearch method to actually search photos from Flickr. It takes PhotoSearchOptions object as parameter and returns PhotoCollection returned by using the search options specified. Finally, I bind the photos collection with the DataList control on the page. Similar to the above method is the GetDescription method which takes photoId as parameter and returns Photo description and other useful information from Flickr website.
private void GetDescription(string photoId)
{
Flickr flickr = new Flickr(flickrKey, sharedSecret);
PhotoInfo info = flickr.PhotosGetInfo(photoId);

PhotoDescription.Text = info.Description;
PhotoDateTaken.Text = info.DateTaken.ToString("MMMM dd, yyyy");
}
Call the above methods in the Page Load event as shown in the code below. Notice how I am getting hidden photoId and photoUrl from the first Item shown in the DataList to make sure user see the first image preview and its description when the page loads first time.
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
string defaultKeyword = "nature";
SearchTextBox.Text = defaultKeyword;
GetPhotos(defaultKeyword);
Literal HiddenPhotoId =
ThumbnailsList.Items[0].FindControl("HiddenPhotoId") as Literal;
Literal HiddenPhotoUrl =
ThumbnailsList.Items[0].FindControl("HiddenPhotoUrl") as Literal;
string photoId = HiddenPhotoId.Text;
string photoUrl = HiddenPhotoUrl.Text;
PreviewImage.ImageUrl = photoUrl;
GetDescription(photoId);
}
}
The same GetPhotos method will be called from the Go button click event to search photos with the user given keyword.
protected void GoButton_Click(object sender, EventArgs e)
{
string keyword = SearchTextBox.Text.Trim();
GetPhotos(keyword);
}
Finally, I am using SelectedIndexChange event of the DataList control to allow user to select any photo by clicking the thumbnail and showing the user selected photo preview and description on the right hand side of the thumbnails.
protected void ThumbnailsList_SelectedIndexChanged(object sender, EventArgs e)
{
Literal HiddenPhotoId =
ThumbnailsList.SelectedItem.FindControl("HiddenPhotoId") as Literal;
Literal HiddenPhotoUrl =
ThumbnailsList.SelectedItem.FindControl("HiddenPhotoUrl") as Literal;
string photoId = HiddenPhotoId.Text;
string photoUrl = HiddenPhotoUrl.Text;
PreviewImage.ImageUrl = photoUrl;
GetDescription(photoId);
}
Download Source Code

Using ASP.NET ImageMap Control

Many web designers try to impress their website visitors with animated flash buttons or crazy JavaScript navigation menus, but they forget the old HTML Image maps. Image maps are images with clickable areas called hotspots, which allow a user to navigate to another page or website. Following the same old HTML concept of image maps, Microsoft introduced the server side ImageMap control for ASP.NET developers that let you convert any image into a navigation menu by just setting few properties. In this tutorial, I will show you how to use ASP.NET server side ImageMap control with Rectangular, Circular or even free form Polygon style hotspots.

Before you start this tutorial, you need to make sure that you have an image ready which you want to use as ImageMap. It can be a toolbar image created in any graphic tool such as Photoshop, or it can be a map of your or home or country. I have created the following image, especially for this tutorial to show you all types of hotspots ASP.NET ImageMap control supports. You can save this image on your desktop and use it for playing with ASP.NET ImageMap control.

ASP.NET ImageMap Control

To get started, create an ASP.NET website project in Visual Studio and add the image in your project root or images sub directory. Next, drag theImageMap control on the page from the left hand side toolbox. Set the ImageUrl property of the control and you will be able to see your image appear on the designer area of the page. If you see the properties of this control in the properties window, you will notice that all the basic properties like BackColor, BorderColor, etc. are available along with ImageAlign and AlternateText properties to fine tune your image look and feel on the page. The properties which need more explanations are HotSpotMode and HotSpots.
HotSpotMode property let you specify the default click behavior of the hotspot inside the ImageMap control. It can be set to one of the followings:
Inactive: This value means that HotSpots does not have any behavior so nothing will happen if the user will click on image.
Navigate: This value allows you to navigate user to any URL.
PostBack: This property allows you to generate post back behavior on user clicks and very useful if you want to execute code on the server side based on the user clicks.
NotSet: This property checks the behavior set by the HotSpotMode property and if none of the above three values are set then all HotSpots navigate to a URL.
Next you need to define the hotspots to divide your image into clickable areas. If you will click the ellipse next to the HotSpots property in the properties window you will see the following HotSpot Collection Editor dialog appear on the screen that lets you specify different types of hotspots. You can add Rectangle, Circle or Polygon hotspots to your image depending upon your image and requirement.

ASP.NET ImageMap Controls Hotspots

All these hotspots types have some properties to customize the hotspot region and behavior. You can specify Left, Top, Right and Bottom for Rectangle hotspot and X, Y and Radius properties for Circle hotspot. The Polygon hotspot requires a serious of X and Y coordinates to create a free form hotspot. All these hotspots types also have HotSpotMode property available to specify their click behavior individually so you can have one hotspot that navigates the user to another page and other hotspot which generate postback to the server and yet another hotspot which does nothing when user click on it. You also have PostBackValue property to send different values to the server on postback. You also haveTarget property to open the URL in a new window if you want and other basic properties such as NavigateUrl to specify the URL to navigate to on user click and AlternateText that will show a nice tool tip when the user will move the mouse over that particular hotspot.
In the sample image I used in this tutorial, the facebook and twitter logos will use navigate behavior while the other four will generate postback to the server. The facebook and twitter logos will use Rectangle hotspots, Wordpress, BMW and Windows logos will use Circle hotspots and the star will show you how to use Polygon hotspot. Following is the complete HTML markup used in this tutorial.

<asp:ImageMap ID="ImageMap1" runat="server" ImageUrl="~/images/aspnet_imagemap.jpg"
OnClick="ImageMap1_Click">
<asp:RectangleHotSpot AlternateText="Facebook" Bottom="62"
HotSpotMode="Navigate" Left="14" NavigateUrl="http://www.facebook.com"
Right="152" Target="_blank" Top="11" />
<asp:RectangleHotSpot AlternateText="Twitter" Bottom="61"
HotSpotMode="Navigate" Left="156" NavigateUrl="http://www.twitter.com"
Right="306" Target="_blank" Top="11" />
<asp:CircleHotSpot AlternateText="WordPress" HotSpotMode="PostBack"
PostBackValue="WordPress" Radius="41" X="50" Y="118" />
<asp:CircleHotSpot AlternateText="BMW" HotSpotMode="PostBack"
PostBackValue="BMW" Radius="41" X="155" Y="121" />
<asp:CircleHotSpot AlternateText="Windows" HotSpotMode="PostBack"
PostBackValue="Windows" Radius="44" X="266" Y="122" />
<asp:PolygonHotSpot AlternateText="Star" HotSpotMode="PostBack"
PostBackValue="Star" Coordinates="108,217, 141,210, 157,181, 173,210, 207,217, 184,242, 188,276, 158,261, 127,275, 131,243" />
</asp:ImageMap>
<br />
<asp:Label ID="Label1" runat="server" Width="322px" BackColor="#FFFFCC" BorderColor="Black"
BorderStyle="Solid" BorderWidth="1px"></asp:Label>

Note, I have also added a Label control at the bottom that will be used to display hotspots PostBackValue on user clicks. The ImageMap control supports click event that allows you to capture the user clicks on different hotspot areas in a single place. It gets the ImageMapEventArgs type object as one of its argument that has PostBackValue property which you can use in the server side code on postback. The following code shows the ImageMap click event handler used in this tutorial.

protected void ImageMap1_Click(object sender, ImageMapEventArgs e)
{
Label1.Text = e.PostBackValue.ToString();
}

Now, It’s the time to test our ImageMap control in the browser, press F5 and try to click different logo hotspots and you will see the Label control showing you the PostBackValue as you will click the logo that has PostBack behavior defined.

ASP.NET Image Map with Postback

SourceCode             Demo

String Format for DateTime

 

This example shows how to format DateTime using String.Format method. All formatting can be done also using DateTime.ToString method.

Custom DateTime Formatting

There are following custom format specifiers y (year), M (month), d (day), h (hour 12), H (hour 24), m (minute), s (second), f (second fraction), F (second fraction, trailing zeroes are trimmed),t (P.M or A.M) and z (time zone).
Following examples demonstrate how are the format specifiers rewritten to the output.
// create date time 2008-03-09 16:05:07.123
DateTime dt = new DateTime(2008, 3, 9, 16, 5, 7, 123);

String.Format("{0:y yy yyy yyyy}", dt); // "8 08 008 2008" year
String.Format("{0:M MM MMM MMMM}", dt); // "3 03 Mar March" month
String.Format("{0:d dd ddd dddd}", dt); // "9 09 Sun Sunday" day
String.Format("{0:h hh H HH}", dt); // "4 04 16 16" hour 12/24
String.Format("{0:m mm}", dt); // "5 05" minute
String.Format("{0:s ss}", dt); // "7 07" second
String.Format("{0:f ff fff ffff}", dt); // "1 12 123 1230" sec.fraction
String.Format("{0:F FF FFF FFFF}", dt); // "1 12 123 123" without zeroes
String.Format("{0:t tt}", dt); // "P PM" A.M. or P.M.
String.Format("{0:z zz zzz}", dt); // "-6 -06 -06:00" time zone

You can use also date separator / (slash) and time sepatator : (colon). These characters will be rewritten to characters defined in the current DateTimeForma­tInfo.DateSepa­rator andDateTimeForma­tInfo.TimeSepa­rator.

// date separator in german culture is "." (so "/" changes to ".")
String.Format("{0:d/M/yyyy HH:mm:ss}", dt); // "9/3/2008 16:05:07" - english (en-US)
String.Format("{0:d/M/yyyy HH:mm:ss}", dt); // "9.3.2008 16:05:07" - german (de-DE)
Here are some examples of custom date and time formatting:

// month/day numbers without/with leading zeroes
String.Format("{0:M/d/yyyy}", dt); // "3/9/2008"
String.Format("{0:MM/dd/yyyy}", dt); // "03/09/2008" // day/month names
String.Format("{0:ddd, MMM d, yyyy}", dt); // "Sun, Mar 9, 2008"
String.Format("{0:dddd, MMMM d, yyyy}", dt); // "Sunday, March 9, 2008" // two/four digit year
String.Format("{0:MM/dd/yy}", dt); // "03/09/08"
String.Format("{0:MM/dd/yyyy}", dt); // "03/09/2008"

Standard DateTime Formatting

In DateTimeForma­tInfo there are defined standard patterns for the current culture. For example property ShortTimePattern is string that contains value h:mm tt for en-US culture and value HH:mm for de-DE culture.
Following table shows patterns defined in DateTimeForma­tInfo and their values for en-US culture. First column contains format specifiers for the String.Format method.
Specifier
DateTimeFormatInfo property
Pattern value (for en-US culture)
t
ShortTimePattern
h:mm tt
d
ShortDatePattern
M/d/yyyy
T
LongTimePattern
h:mm:ss tt
D
LongDatePattern
dddd, MMMM dd, yyyy
f
(combination of D and t)
dddd, MMMM dd, yyyy h:mm tt
F
FullDateTimePattern
dddd, MMMM dd, yyyy h:mm:ss tt
g
(combination of d and t)
M/d/yyyy h:mm tt
G
(combination of d and T)
M/d/yyyy h:mm:ss tt
m, M
MonthDayPattern
MMMM dd
y, Y
YearMonthPattern
MMMM, yyyy
r, R
RFC1123Pattern
ddd, dd MMM yyyy HH':'mm':'ss 'GMT' (*)
s
SortableDateTi­mePattern
yyyy'-'MM'-'dd'T'HH':'mm':'ss (*)
u
UniversalSorta­bleDateTimePat­tern
yyyy'-'MM'-'dd HH':'mm':'ss'Z' (*)
(*) = culture independent
Following examples show usage of standard format specifiers in String.Format method and the resulting output.

String.Format("{0:t}", dt);  // "4:05 PM"                         ShortTime
String.Format("{0:d}", dt);  // "3/9/2008"                        ShortDate
String.Format("{0:T}", dt);  // "4:05:07 PM"                      LongTime
String.Format("{0:D}", dt);  // "Sunday, March 09, 2008"          LongDate
String.Format("{0:f}", dt);  // "Sunday, March 09, 2008 4:05 PM"  LongDate+ShortTime
String.Format("{0:F}", dt);  // "Sunday, March 09, 2008 4:05:07 PM" FullDateTime
String.Format("{0:g}", dt);  // "3/9/2008 4:05 PM"                ShortDate+ShortTime
String.Format("{0:G}", dt);  // "3/9/2008 4:05:07 PM"             ShortDate+LongTime
String.Format("{0:m}", dt);  // "March 09"                        MonthDay
String.Format("{0:y}", dt);  // "March, 2008"                     YearMonth
String.Format("{0:r}", dt);  // "Sun, 09 Mar 2008 16:05:07 GMT"   RFC1123
String.Format("{0:s}", dt);  // "2008-03-09T16:05:07"             SortableDateTime
String.Format("{0:u}", dt);  // "2008-03-09 16:05:07Z"            UniversalSortableDateTime

Posting data to URL in C#.NET

The following procedure describes the steps used to send data to a server. This procedure is commonly used to post data to a Web page.
requestResponse
public static string sendToServer(string Request)
        {
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(“URL”);
               
//HttpWebRequest class is used to Make a request to a Uniform Resource Identifier (URI). 
                request.ContentType = "application/x-www-form-urlencoded";
               // Set the ContentType property of the WebRequest.
                request.Method = "POST";
                byte[] byteArray = Encoding.UTF8.GetBytes(Request);
               // Set the ContentLength property of the WebRequest.
                request.ContentLength = byteArray.Length; 
               //Get the stream that holds request data by calling the GetRequestStream method.
                Stream dataStream = request.GetRequestStream();
                // Write the data to the request stream.
                dataStream.Write(byteArray, 0, byteArray.Length);
                // Close the Stream object.
                dataStream.Close();
                WebResponse response = request.GetResponse();
               // Get the stream containing content returned by the server.

                //Send the request to the server by calling GetResponse.
                dataStream = response.GetResponseStream();
              
// Open the stream using a StreamReader for easy access.
                StreamReader reader = new StreamReader(dataStream);
              
// Read the content.
                string Response = reader.ReadToEnd();
                //return the response
                return Response;
        }



..Source MSDN