private void AddStudentToGroup_Click(object sender, RoutedEventArgs e) { var dg = sender as DataGrid; for (var vis = sender as Visual; vis != null; vis = VisualTreeHelper.GetParent(vis) as Visual) { if (vis is DataGridRow) { if (((System.Windows.FrameworkElement)vis).DataContext is DTOStudent) { var studentId = ((DTO.DTOStudent)((System.Windows.FrameworkElement)vis).DataContext).StudentId; if (studentId != -1) { string answer = client.AddStudentToGroup(studentId, dTOGroup.GroupId); if (answer == "succesfull") { main.Content = new StudentsSomeGroup(client, mw, main, dTOGroup); } } } } } }