Execute reader error? SQLexecutereader not identified?

SqlConnection con = new SqlConnection();
     con.ConnectionString = "Data Source=PROMOD-PC;Initial Catalog=travel_Directions;Integrated Security=True";



     SqlCommand scmd1 = null;
     SqlDataAdapter sDatAdp = new SqlDataAdapter();

     String selQuery = "SELECT Id FROM MapDataImage WHERE Source='" + TextBox1.Text + "';";
             {

             SqlCommand scmd = new SqlCommand(selQuery, con);

             con.Open();

             SqlDataReader sqldread = scmd.ExecuteReader();

             while (sqldread.Read())
             {
                 int Dbid = (int)sqldread["Id"];


                 Label4.Text = Convert.ToString(Dbid);
                 if (Dbid != null)
                 {
                     String QueryStr = "SELECT Image FROM User_Images WHERE Id='" + Dbid + "'";
                     scmd1 = new SqlCommand(QueryStr, con);

                 }
             }

             sqldread.Dispose();
             //scmd1.CommandType = CommandType.Text;
             //scmd1.Connection = con;

         SqlDataReader dr = scmd1.ExecuteReader();
         dr.Read();
         Context.Response.BinaryWrite((byte[])dr["Image"]);
         Context.Response.ContentType = "image/jpg";

         sDatAdp.SelectCommand = scmd1;


         GridView1.DataSource = dr;
         GridView1.DataBind();

         con.Close();
         dr.Close();
         sDatAdp.Dispose();
         con.Dispose();
 }