WPF: How do I make a custom modal dialog flash?

Question

Normally when you open a Modal Dialog and try to click on it\'s parent window the Modal Dialog\'s titlebar flashes. When creating a custom, borderless, chromeless, window in

Answer 1

private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
    {
        var retVal = IntPtr.Zero;

        switch (msg)
        {
            case UnsafeNativeConstants.WM_NCACTIVATE:
                retVal = UnsafeNativeMethods.DefWindowProc(hwnd, UnsafeNativeConstants.WM_NCACTIVATE, new IntPtr(1), new IntPtr(-1));
                AssociatedObject.UpdateTitlebar((int)wParam == 1 ? true : false);
                handled = true;
                break;
        }

        return retVal;
    }

The WndProc I have hooked up in a custom behavior that's attached to my window. It calls an internal method on my window that will update the color of the Titlebar appropriately.

Thanks to @Hans Passant for pointing me in the right direction.

Answer 2

If you didn't exactly find what you're looking for, there is a workaround which involves not using a modal window at all.

Here's how you can do it:

1. create a user control named MainContentUC and put the contents of MainWindow in it

2. create another user control named MessageBoxUC and put the contents of your messagebox in it

   <UserControl x:Name="root" Visibility="{Binding ElementName=root, Path=IsOpen}">
       <Grid Background="#4FFF"/>
           <Border HorizontalAlignment="Center" VerticalAlignment="Center" 
                   x:Name="border" Background="White"/>
           <Grid.Triggers>
               <EventTrigger RoutedEvent="MouseDown">
                   <BeginStoryboard>
                       <Storyboard Duration="0:0:1">
                           <ColorAnimation 
                                Storyboard.TargetName="border" 
                                Storyboard.TargetProperty="(Background).(SolidColorBrush.Color)" 
                                To="Black" Duration="0:0:.2" RepeatBehavior="Forever"/>
                       </Storyboard>
                   </BeginStoryboard>
               </EventTrigger>
           </Grid.Triggers>
       </Grid>
   </UserControl>
   

3. add a boolean dependency property in MessageBoxUC named IsOpen (default=false)

4. write xaml code of your main window as follows:

   <Window xmlns:local="clr-namespace:MyWpfApplication">
       <Grid>
           <local:MainContentsUC/>
           <local:MessageBoxUC/>
       </Grid>
   </Window>
   

This way when the MessageBoxUC is open it will block MainContentsUC from being clicked. and when you click on the back area (where color is set to #4FFF) the trigger runs the storyboard and it blinks.

if you have several windows you can implement different control templates and choose between them using a template selector. so instead of <local:MainContentsUC/> you will have

<ContentPresenter ContentTemplateSelector="{StaticResource mySelector}"/>