Add confirm before closing radwindow.
you can use previewclosed and set WindowPreviewClosedEventArgs's property of cancel true to implement to add confirm before closing radwindow.
void _win_PreviewClosed(object sender,Telerik.Windows.Controls.WindowPreviewClosedEventArgs e)
{
e.Cancel = true;
if (_viewModel.IsEnabledForButtonSave)
{
string confirmText = "Are you sure you want to close without saving?";
RadWindow.Confirm(confirmText, new EventHandler<WindowClosedEventArgs>(OnConfirmWindowClosed));
}
else
{
_proxy.Close();
_mProxy.Close();
_viewModel.BtnCloseClick();
e.Cancel = false;
}
}