updating image in gridview

<asp:GridView ID="GridView1" runat="server" 
              AutoGenerateColumns="False" DataKeyNames="ID"
              DataSourceID="SqlDataSource1">
<Columns>
<asp:BoundField DataField="ID" HeaderText="ID" 
                InsertVisible="False" ReadOnly="True"
                               SortExpression="ID" />
<asp:BoundField DataField="ImageName" HeaderText="ImageName" 
                               SortExpression="ImageName" />
<asp:TemplateField HeaderText="Image">
<ItemTemplate>
<asp:Image ID="Image1" runat="server" 
           ImageUrl='<%# "Handler.ashx?ID=" + Eval("ID")%>'/>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
<asp:SqlDataSource ID="SqlDataSource1" runat="server" 
ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
SelectCommand="SELECT [ID], [ImageName], [Image] 
              FROM [Images]"></asp:SqlDataSource>

<%@ WebHandler Language="C#" Class="Handler" %>
 
using System;
using System.Web;
using System.Configuration;
using System.Data.SqlClient;
 
public class Handler : IHttpHandler {
 
public void ProcessRequest (HttpContext context)
{
SqlConnection con = new SqlConnection();
con.ConnectionString = ConfigurationManager.ConnectionStrings
                      ["ConnectionString"].ConnectionString;
 
// Create SQL Command
SqlCommand cmd = new SqlCommand();
cmd.CommandText = "Select ImageName,Image from Images" +
                  " where ID =@ID";
cmd.CommandType = System.Data.CommandType.Text;
cmd.Connection = con;
 
SqlParameter ImageID = new SqlParameter
                    ("@ID", System.Data.SqlDbType.Int);
ImageID.Value = context.Request.QueryString["ID"];
cmd.Parameters.Add(ImageID);
con.Open();
SqlDataReader dReader = cmd.ExecuteReader();
dReader.Read();
context.Response.BinaryWrite((byte[])dReader["Image"]);
dReader.Close();
con.Close();
}