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Once you ve attached the ObjectDataSource to a class, the next step is to point it to the methods it can use to select and update records. The ObjectDataSource defines SelectMethod, DeleteMethod, UpdateMethod, and InsertMethod properties that you use to link your data access class to various tasks. Each property takes the name of the method in the data access class. In this example, you simply need to enable querying, so you need to set the SelectMethod property: <asp:ObjectDataSource ID="sourceEmployees" runat="server" TypeName="DatabaseComponent.EmployeeDB" SelectMethod="GetEmployees" /> Remember, the GetEmployees() method returns an array of EmployeeDetails objects. These objects fit the criteria of the ObjectDataSource they provide all the appropriate record data through public properties. Once you ve set up the ObjectDataSource, you can bind your web-page controls in the same way you do with the SqlDataSource. You can even use the same drop-down lists in the Properties window, provided you click the Refresh Schema link in the ObjectDataSource smart tag first. When you click Refresh Schema, Visual Studio retrieves the property names and data types by reflecting on the EmployeeDetails class. Here s the complete page code, without the formatting details for the GridView: <asp:ObjectDataSource ID="sourceEmployees" runat="server" TypeName="DatabaseComponent.EmployeeDB" SelectMethod="GetEmployees"/> <asp:ListBox ID="ListBox1" runat="server" DataSourceID="sourceEmployees" DataTextField="EmployeeID"></asp:ListBox> <br /> <asp:GridView ID="GridView1" runat="server" DataSourceID="sourceEmployees"> </asp:GridView> Figure 9-11 shows the result.

public bool IsReusable { get { return true; } } } For this handler to protect image files, you need to register it to deal with the appropriate file types. Here s the web.config settings that set this up for the .gif and .png file types (but not .jpg): <httpHandlers> <add verb="*" path="*.gif" type="ImageGuardHandler"/> <add verb="*" path="*.png" type="ImageGuardHandler"/> </httpHandlers> This works for the integrated Visual Studio web server; however, when you deploy your website, you ll need to take an extra step. Namely, you ll need to add a file mapping in IIS that tells IIS all .gif requests are handled by ASP.NET.

You can improve this situation a fair bit by restricting your use of the SqlDataSource to stored procedures. However, in a large-scale web application, the data access code will be maintained, tested, and refined separately from the business logic (and it may even be coded by different developers). The SqlDataSource just doesn t give you that level of flexibility.

Figure 9-11. Binding to a data access class From the user s perspective, this example is equivalent to the SqlDataSource page shown in Figure 9-8. The only difference is that by default, the columns are shown in the order that the properties are declared in the class, whereas the SqlDataSource shows them in the order they re listed in the query. You can easily change the ordering of columns by customizing the GridView. The apparent similarities conceal some real behind-the-scenes differences. In this example, the web page doesn t require any hard-coded SQL details. Instead, all the work is handed off to the EmployeeDB class. When you run the page, the ListBox and GridView will request data from the ObjectDataSource, which will call the EmployeeDB.GetEmployees() method to retrieve the data (once for each control). This data is then bound and displayed in both controls, with no code required.

This solution to leeching is far from perfect, but it serves to stop casual lechers. A programming-savvy user can easily circumvent it with a little JavaScript code. Some web developers create much more elaborate systems. For example, you can dynamically generate a timestamp code and append it to your image links whenever a page is requested. Your HTTP handler can then refuse to serve images if the timestamp is out-of-date, which suggests the link has been copied and is being reused on another page long after its creation time. However, none of these techniques can stop someone from creating a copy of the picture and serving it directly from their site.