on datagrid edit how to focus on textbox

protected void dgAnnouncement_ItemCommand(object source, DataGridCommandEventArgs e)
{

 switch(e.CommandName)
 {
  case "Edit":
  dg.EditItemIndex = e.Item.ItemIndex;
    . 
    .
                     fillurDataGrid                 
    .                                           
    .                                                                               
  TextBox txtSub1 = (TextBox) dg.Items[e.Item.ItemIndex].Cells[0].FindControl("txtSubject");

     // "Control differ according to the control you used within the DataGrid Column Here me used TextBox"                          
  
  // "Cells[0]    --> "Position Of The Column In The DataGrid"
  
  // "FindControl("txtSubject")  --> Control Id Which Within the Particular Cell
     
  txtSub1.Focus(); 
 }
}