The main idea in this case is to obtain an instance of the GridView class which was clicked. XtraGrid creates clones of the pattern View which is created at design time and use these clones to disply data. Here is the code which should work:
GridView gridView = sender as GridView;
var value = gridView.GetRowCellValue(gridView.FocusedRowHandle, gridView.Columns["Num"));
MessageBox.Show(value.ToString());
Since your child GridView is created automatically, there are two approaches:
1) handle the GridControl's Click event handler:
private void gridControl1_Click(object sender, EventArgs e) {
GridControl grid = sender as GridControl;
Point p = new Point(((MouseEventArgs)e).X, ((MouseEventArgs)e).Y);
GridView gridView = grid.GetViewAt(p) as GridView;
if(gridView != null)
MessageBox.Show(gridView.GetFocusedRowCellDisplayText("Num"));
}
2) handle the GridView1 MasterRowExpanded event handler:
private void gridView1_MasterRowExpanded(object sender, CustomMasterRowEventArgs e) {
GridView master = sender as GridView;
GridView detail = master.GetDetailView(e.RowHandle, e.RelationIndex) as GridView;
detail.Click += new EventHandler(detail_Click);
}
void detail_Click(object sender, EventArgs e) {
GridView gridView = sender as GridView;
var value = gridView.GetRowCellValue(gridView.FocusedRowHandle, gridView.Columns["Num"));
MessageBox.Show(value.ToString());
}