How to use a custom Parameter with SqlDataSource

I want to add a GridView control to one of my views that is backed by a SqlDataSource. The SelectCommand query is parametrized on the aspnet_Users.UserId GUID for the currently-logged-in user, so I need a way to pass the user ID as a parameter.

I read How to utilize ASP.NET current user name in SqlParameter without code-behind and decided to create a custom Parameter named UserIdParameter:

namespace MyApp.Web
{
    public class UserIdParameter : Parameter
    {
        public UserIdParameter(string name)
            : base(name)
        {
        }

        protected UserIdParameter(UserIdParameter parameter)
            : base(parameter)
        {
        }

        protected override Parameter Clone()
        {
            return new UserIdParameter(this);
        }

        protected override object Evaluate(HttpContext context, Control control)
        开发者_如何学编程{
            return Membership.GetUser().ProviderUserKey;
        }
    }
}

In the ASPX view I then added:

<%@ Register TagPrefix="my" Namespace="MyApp.Web" %>

in a line after the <%@ Page ... %> line as well as:

    <SelectParameters>
        <my:UserIdParameter Name="UserId" />
    </SelectParameters>

within the asp:SqlDataSource element.

Unfortunately I get a Parser Error ("An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately.") with the following highlighted in red:

        <my:UserIdParameter Name="UserId" />

Visual Web Developer 2010 Express is also informing me that "Element 'UserIdParameter' is not a known element. This can occur if there is a compilation error in the Web site, or the web.config file is missing."

Do I need to modify Web.config in some way? If not, what do I need to do to be able to use my custom UserIdParameter parameter?

---

I figured out the problem. The custom UserIdParameter class needed to be in a separate assembly and it needed a no-arguments constructor.

The steps that worked for me were:

1. Create a new ASP.NET Server Control project and add it to the current solution. (I named this new project MyApp.Web.UI.WebControls).

2. Add the following class:

   using System.Web;
   using System.Web.Security;
   using System.Web.UI;
   using System.Web.UI.WebControls;
   
   namespace MyApp.Web.UI.WebControls
   {
       public class UserIdParameter : Parameter
       {
           public UserIdParameter()
           {
           }
   
           public UserIdParameter(UserIdParameter userIdParameter)
               : base(userIdParameter)
           {
           }
   
           protected override Parameter Clone()
           {
               return new UserIdParameter(this);
           }
   
           protected override object Evaluate(HttpContext context, Control control)
           {
               return Membership.GetUser().ProviderUserKey;
           }
       }
   }
   

3. Build the MyApp.Web.UI.WebControls assembly. Reference it from the ASP.NET web project (named MyApp.Web in my case).

4. Add to Web.config:

   <pages>
         <controls>
           <add tagPrefix="my" assembly="MyApp.Web.UI.WebControls" namespace="MyApp.Web.UI.WebControls"/>
         </controls>
         <!-- ... -->
   </pages>
   

   This registers the controls library site-wide. (Note that the pages element is within the system.web element.)

5. Use the following in the SelectParameters element of the SqlDataSource:

   <my:UserIdParameter Name="UserGuid" DbType="Guid" />
   

   (No need for <%@ Register ... %>)

---

Why did you don't use SQLDataSource with the parameters in your query ? after that i'm pretty sure that you can tell the SQLDataSource that the parameter @UserId is equal to an session variable. all that without one code line. all in the graphical interface.

---

A more simpler way is to use "Selecting" event. here you can add your custom parameter.

http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.sqldatasource.selecting.aspx