how to do update images in gridview by select a link button

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C#

ASP.NET

pls some one one tell that how to do updation in gridview of images, i am able to do updation in text and fill to text boxes outside the gridview but how should i do for images my code is

protected void showDataTable()
   {
       //DataTable dt = dbHelper.returnDataTable("select * from Emp_Mast where E_Id='" + ViewState["id"] + "' and isDeleted=0");

       SqlCommand cmd = new SqlCommand("select * from tbl_Products",con);
       SqlDataAdapter DA = new SqlDataAdapter(cmd);
       DataTable dt = new DataTable();
       DA.Fill(dt);
       if (dt.Rows.Count > 0)
       {
           txttitle.Text = dt.Rows[0]["Title"].ToString().Trim();
           txtdescrip.Text = dt.Rows[0]["description"].ToString().Trim();
           txtUserId.Text = dt.Rows[0]["E_Login"].ToString().Trim();
           //txtPassword.Text = dt.Rows[0]["E_Pwd"].ToString().Trim();
           txtPassword.Text = "*****";
           txtUserId.ReadOnly = true;
           txtPassword.ReadOnly = true;
           //ddlBranch.SelectedValue=int.Parse(dt.Rows[0]["B_Id"].ToString());
           string mc = dt.Rows[0]["B_Id"].ToString();
           try
           {
               ddlBranch.SelectedValue = mc;
           }
           catch
           {
               ddlBranch.SelectedIndex = 0;
           }

       }

pls some one tell for images.....