ASP.NET 4 Unleased - p 81 pdf

Binding to a DataReader Typically, you use the ObjectDataSource control to represent database data.. For example, the component in Listing 18.3, the MovieDataReader component, returns al

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In Listing 18.2, the ObjectDataSource control includes two properties named TypeName

and SelectMethod The TypeName property contains the name of the component that you

want to represent with the ObjectDataSource control The SelectMethod property

repre-sents the method of the component that you want to call when selecting data

The GridView control is bound to the ObjectDataSource control through its DataSourceID

property When you open the page in Listing 18.2, the list of movies is retrieved from the

MovieCollection component and displayed in the GridView

The MovieCollection component contains instance methods The ObjectDataSource

automatically creates a new instance of the MovieCollection component before calling its

GetMovies() method It automatically destroys the object after it finishes using the object

You also can use the ObjectDataSource control to call shared (static) methods In that

case, the ObjectDataSource doesn’t need to instantiate a component before calling the

method

Binding to a DataReader

Typically, you use the ObjectDataSource control to represent database data The NET

Framework provides you with multiple ways of representing data This section discusses

how you can use an ObjectDataSource to represent a DataReader

NOTE

The different ADO.NET objects are compared and contrasted in Chapter 19, “Building

Data Access Components with ADO.NET.”

The ADO.NET DataReader object provides you with a fast, read-only representation of

database data If you need to retrieve database records in the fastest possible way, you

should use a DataReader object

For example, the component in Listing 18.3, the MovieDataReader component, returns all

the movies from the Movies database table by using the SqlDataReader object The

component imports the System.Data.SqlClient namespace to use this Microsoft SQL

Server-specific ADO.NET object

LISTING 18.3 MovieDataReader.cs

using System;

using System.Data;

using System.Data.SqlClient;

using System.Web.Configuration;

public class MovieDataReader

{

private readonly string _conString;

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public SqlDataReader GetMovies()

{

// Create Connection

SqlConnection con = new SqlConnection(_conString);

// Create Command

SqlCommand cmd = new SqlCommand();

cmd.Connection = con;

cmd.CommandText = “SELECT Id,Title,Director FROM Movies”;

// Return DataReader

con.Open();

return cmd.ExecuteReader(CommandBehavior.CloseConnection);

}

public MovieDataReader()

{

_conString =

➥WebConfigurationManager.ConnectionStrings[“Movies”].ConnectionString;

}

The component in Listing 18.3 actually uses three ADO.NET objects: Connection, Command,

and DataReader The SqlCommand object uses the SqlConnection object to connect to the

database The records are returned from the SqlCommand object and represented by the

SqlDataReader object

The WebConfigurationManager class retrieves the database connection string from the web

configuration file To use this class, you need to import the System.Web.Confiugration

namespace (and have a reference to the System.Web.dll assembly)

The ObjectDataSource control in Listing 18.4 represents the MovieDataReader object It

binds the movies to a GridView control

LISTING 18.4 ShowMovieDataReader.aspx

<%@ Page Language=”C#” %>

<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.1//EN”

“http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd”>

<title>Show Movie DataReader</title>

</head>

<body>

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<div>

<asp:GridView

id=”grdMovies”

DataSourceID=”srcMovies”

Runat=”server” />

<asp:ObjectDataSource

id=”srcMovies”

TypeName=”MovieDataReader”

SelectMethod=”GetMovies”

</div>

</form>

</body>

</html>

Binding to a DataSet

You also can use the ObjectDataSource when you need to represent an ADO.NET

DataSet Using a DataSet is slower than using a DataReader; however, you can perform

advanced operations, such as filtering and sorting, on data represented with a DataSet

The component in Listing 18.5 returns all the records from the Movies database table

However, it uses a DataSet instead of a DataReader object

LISTING 18.5 MovieDataSet.cs

using System;

using System.Data;

public class MovieDataSet

{

private readonly string _conString;

public DataSet GetMovies()

{

// Create DataAdapter

string commandText = “SELECT Id,Title,Director FROM Movies”;

SqlDataAdapter dad = new SqlDataAdapter(commandText, _conString);

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// Return DataSet

DataSet dstMovies = new DataSet();

using (dad)

{

dad.Fill(dstMovies);

}

return dstMovies;

}

public MovieDataSet()

{

_conString =

➥WebConfigurationManager.ConnectionStrings[“Movies”].ConnectionString;

}

The component in Listing 18.5 uses two ADO.NET objects: DataAdapter and DataSet The

SqlDataAdapter represents the SQL select command and populates the DataSet with the

results of executing the command The WebConfigurationManager class reads the database

connection string from the web configuration file

The page in Listing 18.6 binds the list of movies to a DropDownList control

LISTING 18.6 ShowMovieDataSet.aspx

<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.1//EN”

“http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd”>

<title>Show Movie DataSet</title>

</head>

<body>

<div>

<asp:GridView

id=”grdMovies”

DataSourceID=”srcMovies”

id=”srcMovies”

TypeName=”MovieDataReader”

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SelectMethod=”GetMovies”

</div>

</form>

</body>

</html>

Binding to a LINQ to SQL Query

LINQ to SQL is the preferred method of data access in NET Framework The expectation is

that you will use LINQ to SQL instead of ADO.NET to interact with a database Chapter

20, “Data Access with LINQ to SQL,” is devoted to the topic of LINQ to SQL

Here’s a quick sample of binding an ObjectDataSource to a component that represents a

LINQ to SQL query The component that contains the LINQ query is contained in

Listing 18.7

LISTING 18.7 Employee.cs

using System.Collections.Generic;

using System.Linq;

using System.Data.Linq;

public partial class Employee

{

public static IEnumerable<Employee> Select()

{

EmployeesDataContext db = new EmployeesDataContext();

return db.Employees.OrderBy( e=>e.LastName );

}

Before you can use the component in Listing 18.7, you first must create the

EmployeesDataContext The easiest way to create the DataContext is to select Website,

Add New Item and select the LINQ to SQL Classes template Name the LINQ to SQL

Classes Employees.

After the LINQ to SQL Designer appears, drag the Employees database table onto the

Designer surface from the Database Explorer window At this point, the

EmployeesDataContext will be ready

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The page in Listing 18.8 contains an ObjectDataSource that represents the Employee class

LISTING 18.8 ShowLINQ.aspx

<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//EN”

“http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd”>

</head>

<body>

<div>

<asp:GridView

id=”grdEmployees”

DataSourceID=”srcEmployees”

runat=”server” />

id=”srcEmployees”

TypeName=”Employee”

SelectMethod=”Select”

</div>

</form>

</body>

</html>

Binding to a Web Service

Web services enable you to share information across the Internet When you

communi-cate with a remote web service, you use a local proxy class to represent the web service

located on the remote machine You can use the ObjectDataSource to represent this proxy

class

For example, the file in Listing 18.9 contains a simple web service that returns the current

server time You can create this file in Visual Web Developer by selecting Web Site, Add

New Item, and selecting the Web Service item

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LISTING 18.9 TimeService.asmx

<%@ WebService Language=”C#” Class=”TimeService” %>

using System;

using System.Web;

using System.Web.Services;

using System.Web.Services.Protocols;

[WebService(Namespace = “http://tempuri.org/”)]

[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]

public class TimeService : System.Web.Services.WebService {

[WebMethod]

public DateTime GetServerTime() {

return DateTime.Now;

}

After you create the web service in Listing 18.9, you can communicate with the service

from anywhere in the world (or the galaxy or the universe) Just as long as a computer is

connected to the Internet, the computer can call the GetServerTime() method

Before you can call the web service, you need to create a web service proxy class If you

use Visual Web Developer, select Web Site, Add Web Reference and enter the URL of the

TimeService.asmx file (You can click the Web Services in This Solution link to list all the

web services in your current project.) Change the name of the web reference to

LocalServices and click Add Reference (see Figure 18.1)

NOTE

If you are not using Visual Web Developer, you can create a web service proxy class

from the command line by using the Wsdl.exe (Web Services Description Language)

tool

When you click Add Reference, a new folder is added to your project named

App_WebReferences The App_WebReferences folder contains a subfolder named

LocalServices Finally, your web configuration file is updated to include the URL to the

TimeService web service

Now that we have a consumable web service, we can represent the Web service using the

ObjectDataSource control The page in Listing 18.10 displays the server time using a

FormView control bound to an ObjectDataSource control (see Figure 18.2)

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FIGURE 18.1 Adding a Web Reference in Visual Web Developer

FIGURE 18.2 Retrieving the time from a web service

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LISTING 18.10 ShowWebService.aspx

html

{

background-color:silver;

}

.serverTime

{

background-color:white;

font:16px Georgia,Serif;

}

.serverTime td

{

padding:40px;

}

</style>

<title>Show Web Service</title>

</head>

<body>

<div>

<asp:FormView

id=”frmServerTime”

DataSourceID=”srcServerTime”

CssClass=”serverTime”

Runat=”server”>

The remote server date and time is: <%# Container.DataItem %>

</ItemTemplate>

</asp:FormView>

id=”srcServerTime”

TypeName=”LocalServices.TimeService”

SelectMethod=”GetServerTime”

</div>

</form>

</body>

</html>

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The ObjectDataSource control’s TypeName property contains both the namespace and

name of the web service proxy class (the web reference) In other words, it contains the

fully qualified name of the proxy class The SelectMethod property contains the name of

the web method represented by the proxy class

NOTE

If you open the ShowWebService.aspx page from the book’s website, you receive an

error Before the page will work correctly, you need to update the web configuration file

with the correct path to the web service on your computer

Control

You can use parameters when calling a method with the ObjectDataSource control The

ObjectDataSource control includes five parameter collections:

SelectParameters—Collection of parameters passed to the method represented by

the SelectMethod property

InsertParameters—Collection of parameters passed to the method represented by

the InsertMethod property

UpdateParameters—Collection of parameters passed to the method represented by

the UpdateMethod property

DeleteParameters—Collection of parameters passed to the method represented by

the DeleteParameters property

FilterParameters—Collection of parameters used by the FilterExpression property

DataBound controls—such as the GridView, DetailsView, and FormView controls—can

build the necessary parameter collections for you automatically

For example, the component in Listing 18.11 enables you to select movies and update a

particular movie in the Movies database table The UpdateMovie() method has four

parameters: id, title, director, and dateReleased

LISTING 18.11 Movies.cs

using System;

using System.Data;

public class Movies

{

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