How to access control which are dynamically added inside Gridview?

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
  {
       if (e.Row.RowType == DataControlRowType.DataRow)
       {
           DataRowView drv = (DataRowView)e.Row.DataItem;
           if (drv != null)
           {
               Literal ltr = e.Row.FindControl("ltr") as Literal;
               ltr.Text = drv.Row["Id"].ToString();
               if (e.Row.RowIndex == 0)
               {
                   TextBox oTB = new TextBox();
                   oTB.ID = "TextBox1";
                   e.Row.Cells[1].Controls.Add(oTB);
                   oTB = null;
               }
               if (e.Row.RowIndex == 1)
               {
                   Panel p1 = new Panel();
                   p1.Width = Unit.Pixel(500);
                   p1.Height = Unit.Pixel(200);
                   p1.ScrollBars = ScrollBars.Vertical;
                   CheckBoxList cbl = new CheckBoxList();
                   cbl.ID = "cbl";
                   cbl.RepeatColumns = 2;
                   cbl.Items.Add(new ListItem("JAKARTA", "JKT"));
                   cbl.Items.Add(new ListItem("Maharashtra", "MH"));
                   p1.Controls.Add(cbl);
                   e.Row.Cells[1].Controls.Add(p1);
               }
           }
       }
   }

foreach (GridViewRow row in GridView1.Rows)
       {
           TextBox txt = row.FindControl("TextBox1") as TextBox;
           CheckBoxList cbl = row.FindControl("cbl") as CheckBoxList;   
       }