I am trying to work with gridview but it gives me the following error (on binding) : [B]Exception Details: [FONT=Arial]System.Web.HttpException: The DataSourceID of 'GridView1' must be the ID of a control of type IDataSource. A control with ID 'grade' could not be found.[/FONT] [/B] Code (markup): This is my client code: <%@ Page Title="" Language="C#" MasterPageFile="~/master.Master" AutoEventWireup="true" CodeBehind="GradesDisplay.aspx.cs" Inherits="Project2012.GradesDisplay" %><asp:Content ID="Content1" ContentPlaceHolderID="head" runat="server"></asp:Content><asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="server"> <asp:GridView ID="GridView1" runat="server" DataSourceID="JTutor2.grade" Height="128px" Width="305px" AllowPaging="True" AllowSorting="True" CellPadding="4" ForeColor="#333333" GridLines="None"> <AlternatingRowStyle BackColor="White" /> <EditRowStyle BackColor="#2461BF" /> <FooterStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" /> <HeaderStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" /> <PagerStyle BackColor="#2461BF" ForeColor="White" HorizontalAlign="Center" /> <RowStyle BackColor="#EFF3FB" /> <SelectedRowStyle BackColor="#D1DDF1" Font-Bold="True" ForeColor="#333333" /> <SortedAscendingCellStyle BackColor="#F5F7FB" /> <SortedAscendingHeaderStyle BackColor="#6D95E1" /> <SortedDescendingCellStyle BackColor="#E9EBEF" /> <SortedDescendingHeaderStyle BackColor="#4870BE" /> </asp:GridView> <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:JTutor2 %>" SelectCommand="SELECT grade.User_ID, grade.Grade_date, grade.Grade_grade, Lesson.lesson_name FROM grade INNER JOIN Lesson ON grade.Lesson_ID = Lesson.ID WHERE (grade.User_ID = @user_id)"> <SelectParameters> <asp:Parameter Name="user_id" /> </SelectParameters> </asp:SqlDataSource> </asp:Content> HTML: And this is my server code: User usr=(User)Session["User"]; SqlDataSource1.SelectParameters["User_id"].DefaultValue = usr.User_ID; Code (markup):