Custom Server Controls :: Extend A Datagrid Control And Use It In Program

I want to extend a datagrid control and use it in my program.

public class MyDataGrid : DataGrid
{}

Now i want to make use this new control in my web page. so i need to register this user control in page.

<%@
Register
TagPrefix
="sam"
Namespace="WebApplication1"
%>
<form><sam:MyDataGrid id="test" runat="server" /> </form>

When I build it is fine. When i run the application it throws the error.

MyDataGrid is a unknown element.This error occurs due to compilation error or web.config does not exists. But there was no scenario like this.

Unknown server tag 'sam:MyDataGrid.Error occured due to parsing.