ASP.NET 4 Unleased - p 81 pdf

ptg 774 CHAPTER 18 Using the ObjectDataSource Control 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 represents 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; From the Library of Wow! eBook ptg 775 Representing Objects with the ObjectDataSource Control 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”> <html xmlns=”http://www.w3.org/1999/xhtml” > <head id=”Head1” runat=”server”> <title>Show Movie DataReader</title> </head> <body> <form id=”form1” runat=”server”> 18 From the Library of Wow! eBook ptg 776 CHAPTER 18 Using the ObjectDataSource Control <div> <asp:GridView id=”grdMovies” DataSourceID=”srcMovies” Runat=”server” /> <asp:ObjectDataSource id=”srcMovies” TypeName=”MovieDataReader” SelectMethod=”GetMovies” Runat=”server” /> </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; using System.Data.SqlClient; using System.Web.Configuration; 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); From the Library of Wow! eBook ptg 777 Representing Objects with the ObjectDataSource Control // 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 <%@ Page Language=”C#” %> <!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.1//EN” “http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd”> <html xmlns=”http://www.w3.org/1999/xhtml” > <head id=”Head1” runat=”server”> <title>Show Movie DataSet</title> </head> <body> <form id=”form1” runat=”server”> <div> <asp:GridView id=”grdMovies” DataSourceID=”srcMovies” Runat=”server” /> <asp:ObjectDataSource id=”srcMovies” TypeName=”MovieDataReader” 18 From the Library of Wow! eBook ptg 778 CHAPTER 18 Using the ObjectDataSource Control SelectMethod=”GetMovies” Runat=”server” /> </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. From the Library of Wow! eBook ptg 779 Representing Objects with the ObjectDataSource Control The page in Listing 18.8 contains an ObjectDataSource that represents the Employee class. LISTING 18.8 ShowLINQ.aspx <%@ Page Language=”C#” %> <!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>Show LINQ</title> </head> <body> <form id=”form1” runat=”server”> <div> <asp:GridView id=”grdEmployees” DataSourceID=”srcEmployees” runat=”server” /> <asp:ObjectDataSource id=”srcEmployees” TypeName=”Employee” SelectMethod=”Select” Runat=”server” /> </div> </form> </body> </html> Binding to a Web Service Web services enable you to share information across the Internet. When you communicate 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. 18 From the Library of Wow! eBook ptg 780 CHAPTER 18 Using the ObjectDataSource Control 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). From the Library of Wow! eBook ptg 781 Representing Objects with the ObjectDataSource Control 18 FIGURE 18.1 Adding a Web Reference in Visual Web Developer. FIGURE 18.2 Retrieving the time from a web service. From the Library of Wow! eBook ptg 782 CHAPTER 18 Using the ObjectDataSource Control LISTING 18.10 ShowWebService.aspx <%@ Page Language=”C#” %> <html xmlns=”http://www.w3.org/1999/xhtml” > <head id=”Head1” runat=”server”> <style type=”text/css”> html { background-color:silver; } .serverTime { background-color:white; font:16px Georgia,Serif; } .serverTime td { padding:40px; } </style> <title>Show Web Service</title> </head> <body> <form id=”form1” runat=”server”> <div> <asp:FormView id=”frmServerTime” DataSourceID=”srcServerTime” CssClass=”serverTime” Runat=”server”> <ItemTemplate> The remote server date and time is: <%# Container.DataItem %> </ItemTemplate> </asp:FormView> <asp:ObjectDataSource id=”srcServerTime” TypeName=”LocalServices.TimeService” SelectMethod=”GetServerTime” Runat=”server” /> </div> </form> </body> </html> From the Library of Wow! eBook ptg 783 Using Parameters with the ObjectDataSource Control 18 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. Using Parameters with the ObjectDataSource 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; using System.Data.SqlClient; using System.Web.Configuration; public class Movies { private readonly string _conString; From the Library of Wow! eBook . 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. method represented by the SelectMethod property. . InsertParameters—Collection of parameters passed to the method represented by the InsertMethod property. . UpdateParameters—Collection of parameters. ObjectDataSource that represents the Employee class. LISTING 18.8 ShowLINQ.aspx <%@ Page Language=”C#” %> <!DOCTYPE html PUBLIC -/ /W3C//DTD XHTML 1.0 Transitional//EN” “http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd”>