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ptg 404 CHAPTER 9 Using the SqlDataSource Control LISTING 9.14 CancelCommand.aspx <%@ Page Language=”C#” %> <%@ Import Namespace=”System.Data.SqlClient” %> <!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.1//EN” “http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd”> <script runat=”server”> /// <summary> /// Iterate through all parameters and check for null /// </summary> protected void srcMovies_Updating(object sender, SqlDataSourceCommandEventArgs e) { foreach (SqlParameter param in e.Command.Parameters) if (param.Value == null) { e.Cancel = true; lblError.Text = “All fields are required!”; } } </script> <html xmlns=”http://www.w3.org/1999/xhtml” > <head id=”Head1” runat=”server”> FIGURE 9.8 Canceling a command when a field is blank. From the Library of Wow! eBook ptg 405 Executing Database Commands 9 <style type=”text/css”> .error { display:block; color:red; font:bold 16px Arial; margin:10px; } td,th { padding:10px; } </style> <title>Cancel Command</title> </head> <body> <form id=”form1” runat=”server”> <div> <asp:Label id=”lblError” EnableViewState=”false” CssClass=”error” Runat=”server” /> <asp:DetailsView id=”dtlMovie” DataSourceID=”srcMovies” DataKeyNames=”Id” AllowPaging=”true” AutoGenerateEditButton=”true” Runat=”server” /> <asp:SqlDataSource id=”srcMovies” SelectCommand=”SELECT * FROM Movies” UpdateCommand=”UPDATE Movies SET Title=@Title, Director=@Director,DateReleased=@DateReleased WHERE Id=@id” ConnectionString=”<%$ ConnectionStrings:Movies %>” Runat=”server” OnUpdating=”srcMovies_Updating” /> </div> </form> </body> </html> From the Library of Wow! eBook ptg 406 CHAPTER 9 Using the SqlDataSource Control The page in Listing 9.14 includes a srcMovies_Updating() method. In this method, each parameter associated with the update command is compared against the value Nothing (null). If one of the parameters is null, an error message displays in a Label control. Using ASP.NET Parameters with the SqlDataSource Control You can use any of the following ASP.NET Parameter objects with the SqlDataSource control: . Parameter—Represents an arbitrary static value. . ControlParameter—Represents the value of a control or page property. . CookieParameter—Represents the value of a browser cookie. . FormParameter—Represents the value of an HTML form field. . ProfileParameter—Represents the value of a Profile property. . QueryStringParameter—Represents the value of a query string field. . SessionParameter—Represents the value of an item stored in Session state. The SqlDataSource control includes five collections of ASP.NET parameters: SelectParameters, InsertParameters, DeleteParameters, UpdateParameters, and FilterParameters. You can use these parameter collections to associate a particular ASP.NET parameter with a particular SqlDataSource command or filter. In the following sections, you learn how to use each of these different types of parameter objects. Using the ASP.NET Parameter Object The ASP.NET parameter object has the following properties: . ConvertEmptyStringToNull—When true, if a parameter represents an empty string, the empty string converts to the value Nothing (null) before the associated command executes. . DefaultValue—When a parameter has the value Nothing (null), the DefaultValue is used for the value of the parameter. . Direction—Indicates the direction of the parameter. Possible values are Input, InputOutput, Output, and ReturnValue. . Name—Indicates the name of the parameter. Do not use the @ character when indi- cating the name of an ASP.NET parameter. . Size—Indicates the data size of the parameter. From the Library of Wow! eBook ptg 407 Using ASP.NET Parameters with the SqlDataSource Control 9 . Type—Indicates the .NET Framework type of the parameter. You can assign any value from the TypeCode enumeration to this property. You can use the ASP.NET parameter object to indicate several parameter properties explic- itly, such as a parameter’s type, size, and default value. For example, the page in Listing 9.15 contains a DetailsView control bound to a SqlDataSource control. You can use the page to update records in the Movies database table (see Figure 9.9). FIGURE 9.9 Updating movie records. LISTING 9.15 ShowDetailsView.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 DetailsView</title> </head> <body> <form id=”form1” runat=”server”> <div> <asp:DetailsView From the Library of Wow! eBook ptg 408 CHAPTER 9 Using the SqlDataSource Control id=”dtlMovie” DataKeyNames=”Id” DataSourceID=”srcMovies” AutoGenerateEditButton=”true” DefaultMode=”Edit” AllowPaging=”true” runat=”server” /> <asp:SqlDataSource id=”srcMovies” ConnectionString=”<%$ ConnectionStrings:Movies %>” SelectCommand=”Select * FROM Movies” UpdateCommand=”UPDATE Movies SET Title=@Title,Director=@Director, DateReleased=@DateReleased WHERE Id=@id” Runat=”server” /> </div> </form> </body> </html> In Listing 9.15, no ASP.NET parameter objects are declared explicitly. The DetailsView control automatically creates and adds ADO.NET parameters to the SqlDataSource control’s update command before the command is executed. If you want to be explicit about the data types and sizes of the parameters used by a SqlDataSource control, you can declare the parameters. The page in Listing 9.16 declares each of the parameters used when executing the update command. LISTING 9.16 ShowDetailsViewExplicit.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 DetailsView Explicit</title> </head> <body> <form id=”form1” runat=”server”> <div> From the Library of Wow! eBook ptg 409 Using ASP.NET Parameters with the SqlDataSource Control 9 <asp:DetailsView id=”dtlMovie” DataKeyNames=”Id” DataSourceID=”srcMovies” AutoGenerateEditButton=”true” DefaultMode=”Edit” AllowPaging=”true” runat=”server” /> <asp:SqlDataSource id=”srcMovies” ConnectionString=”<%$ ConnectionStrings:Movies %>” SelectCommand=”Select * FROM Movies” UpdateCommand=”UPDATE Movies SET Title=@Title,Director=@Director, DateReleased=@DateReleased WHERE Id=@id” Runat=”server”> <UpdateParameters> <asp:Parameter Name=”Title” Type=”String” Size=”100” DefaultValue=”Untitled” /> <asp:Parameter Name=”Director” Type=”String” Size=”100” DefaultValue=”Alan Smithee” /> <asp:Parameter Name=”DateReleased” Type=”DateTime” /> <asp:Parameter Name=”id” Type=”int32” /> </UpdateParameters> </asp:SqlDataSource> </div> </form> </body> </html> In Listing 9.16, each of the parameters used by the update command is provided with an explicit data type. For example, the DateReleased parameter is declared to be a DateTime parameter. (If you didn’t assign an explicit type to this parameter, it would default to a string.) Furthermore, the Title and Director parameters are provided with default values. If you edit a movie record and do not supply a title or director, the default values are used. NOTE Another situation in which explicitly declaring Parameter objects is useful is when you need to explicitly order the parameters. For example, the order of parameters is impor- tant when you use the OLE DB provider with Microsoft Access. From the Library of Wow! eBook ptg 410 CHAPTER 9 Using the SqlDataSource Control Using the ASP.NET ControlParameter Object You use the ControlParameter object to represent the value of a control property. You can use it to represent the value of any control contained in the same page as the SqlDataSource control. The ControlParameter object includes all the properties of the Parameter object and these additional properties: . ControlID—The ID of the control that the parameter represents. . PropertyName—The name of the property that the parameter represents. For example, the page in Listing 9.17 includes a DropDownList control and a DetailsView control. When you select a movie from the DropDownList, details for the movie display in the DetailsView control (see Figure 9.10). LISTING 9.17 ShowControlParameter.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 Control Parameter</title> FIGURE 9.10 Show matching movies for each movie category. From the Library of Wow! eBook ptg 411 Using ASP.NET Parameters with the SqlDataSource Control 9 </head> <body> <form id=”form1” runat=”server”> <div> <asp:DropDownList id=”ddlMovies” DataSourceID=”srcMovies” DataTextField=”Title” DataValueField=”Id” Runat=”server” /> <asp:Button id=”btnSelect” Text=”Select” Runat=”server” /> <hr /> <asp:DetailsView id=”dtlMovie” DataSourceID=”srcMovieDetails” Runat=”server” /> <asp:SqlDataSource id=”srcMovies” SelectCommand=”SELECT Id,Title FROM Movies” ConnectionString=”<%$ ConnectionStrings:Movies %>” Runat=”server” /> <asp:SqlDataSource id=”srcMovieDetails” SelectCommand=”SELECT * FROM Movies WHERE Id=@Id” ConnectionString=”<%$ ConnectionStrings:Movies %>” Runat=”server”> <SelectParameters> <asp:ControlParameter Name=”Id” ControlID=”ddlMovies” PropertyName=”SelectedValue” /> </SelectParameters> </asp:SqlDataSource> </div> </form> </body> </html> From the Library of Wow! eBook ptg 412 CHAPTER 9 Using the SqlDataSource Control The second SqlDataSource control in Listing 9.17 includes a ControlParameter object. The ControlParameter represents the ID of the selected movie in the DropDownList control. When using a ControlParameter, you must always set the value of the ControlID property to point to a control on the page. On the other hand, you are not always required to set the PropertyName property. If you do not set PropertyName, the ControlParameter object automatically looks for a property decorated with the ControlValueProperty attribute. Because the SelectedValue property of the DropDownList control is decorated with this attribute, you do not need to set this property in Listing 9.17. Because the Page class derives from the control class, you can use the ControlParameter object to represent the value of a Page property. For example, the page in Listing 9.18 contains a simple guestbook that connects to a data- base called “GuestBook”. When a user adds a new entry to the guestbook, the user’s remote IP address is saved automatically with the guestbook entry (see Figure 9.11). FIGURE 9.11 Saving an IP address in guest book entries. From the Library of Wow! eBook ptg 413 Using ASP.NET Parameters with the SqlDataSource Control 9 LISTING 9.18 ShowPageControlParameter.aspx <%@ Page Language=”C#” %> <!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.1//EN” “http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd”> <script runat=”server”> public string IPAddress { get { return Request.UserHostAddress; } } </script> <html xmlns=”http://www.w3.org/1999/xhtml” > <head id=”Head1” runat=”server”> <title>Show Page Control Parameter</title> </head> <body> <form id=”form1” runat=”server”> <div> <asp:FormView id=”frmGuestBook” DataSourceID=”srcGuestBook” DefaultMode=”Insert” runat=”server”> <InsertItemTemplate> <asp:Label id=”lblName” Text=”Your Name:” AssociatedControlID=”txtName” Runat=”server” /> <asp:TextBox id=”txtName” Text=’<%# Bind(“Name”) %>’ Runat=”server” /> <br /><br /> <asp:Label id=”Label1” Text=”Your Comments:” AssociatedControlID=”txtComments” Runat=”server” /> <br /> <asp:TextBox id=”txtComments” From the Library of Wow! eBook . of ASP. NET parameters: SelectParameters, InsertParameters, DeleteParameters, UpdateParameters, and FilterParameters. You can use these parameter collections to associate a particular ASP. NET. to this property. You can use the ASP. NET parameter object to indicate several parameter properties explic- itly, such as a parameter’s type, size, and default value. For example, the page in Listing. eBook ptg 40 7 Using ASP. NET Parameters with the SqlDataSource Control 9 . Type—Indicates the .NET Framework type of the parameter. You can assign any value from the TypeCode enumeration to this property. You
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