please solve the following Issue

if (e.CommandName == "ImageButton2_Click")
{
   int rowindex = Convert.ToInt32(e.CommandArgument);
   //Get Row
   GridViewRow gvr = GridView2.Rows[rowindex];
   {
      Label ID = (Label)GridView2.Rows[rowindex].Cells[1].FindControl("Role_ID");
      string Role_ID = ID.Text;
      con.Open();

      using (SqlCommand comm = new SqlCommand("select [UserName] from Login where Role_ID =@Role", con))
      {
         // 2. define parameters used in command object
         SqlParameter para = null;
         para = new SqlParameter();
         para.ParameterName = "@Role";
         para.Value = Role_ID;
         comm.Parameters.Add(para);
         SqlDataReader reade = comm.ExecuteReader();
         ImageButton button =
            (ImageButton)GridView2.Rows[rowindex].Cells[5].FindControl("ImageButton2");
         button.Visible = false;
                   
         ArrayList yourList = new ArrayList();
         if (reade.HasRows)
         {
            if (reade != null)
            {
               while (reade.Read())
               {
                  //ImageButton button =(ImageButton)GridView2.Rows[rowindex].Cells[5].FindControl("ImageButton2");
                  button.Visible = true;
                   
                  yourList.Add(Convert.ToString(reade[0]));
                  Session["UserName"] = yourList[0];
               }
            }
         }
      }
      if (Session["UserName"].ToString() == null)
      {
         ImageButton button =
            (ImageButton)GridView2.Rows[rowindex].Cells[5].FindControl("ImageButton2");
         button.Visible = false;
      }
      else
      {
         ImageButton button =
            (ImageButton)GridView2.Rows[rowindex].Cells[5].FindControl("ImageButton2");
         button.Visible = true;

         ClientScript.RegisterStartupScript(this.GetType(), "myalert", "alert('" + Session["UserName"].ToString() + "');", true);

         con.Close();
      }
   }
}