How to make a WPF Window to blink on the taskbar?

Question

A given moment my WPF app needs user attention. I know it is possible to make the Windows 7 taskbar icon to flash with a yellow color.

I tried so far:

Answer 1

As proposed by Kate, I used taskbar progress like this:

XAML:

<Window.TaskbarItemInfo>
   <TaskbarItemInfo x:Name="taskBarItem"/>
</Window.TaskbarItemInfo>

cs:

taskBarItem.ProgressState = System.Windows.Shell.TaskbarItemProgressState.Indeterminate;

This makes the taskbar icon blink in green, which was good enough for my use case to get the users attention to a long running application.

Answer 2

Here's one possible solution: http://www.jarloo.com/flashing-a-wpf-window/

In the code sample, two extensions methods are created for the Window class: FlashWindow and StopFlashingWindow:

private const UInt32 FLASHW_STOP = 0; //Stop flashing. The system restores the window to its original state.        private const UInt32 FLASHW_CAPTION = 1; //Flash the window caption.        
private const UInt32 FLASHW_TRAY = 2; //Flash the taskbar button.        
private const UInt32 FLASHW_ALL = 3; //Flash both the window caption and taskbar button.        
private const UInt32 FLASHW_TIMER = 4; //Flash continuously, until the FLASHW_STOP flag is set.        
private const UInt32 FLASHW_TIMERNOFG = 12; //Flash continuously until the window comes to the foreground.  


[StructLayout(LayoutKind.Sequential)]        
private struct FLASHWINFO        
{            
    public UInt32 cbSize; //The size of the structure in bytes.            
    public IntPtr hwnd; //A Handle to the Window to be Flashed. The window can be either opened or minimized.


    public UInt32 dwFlags; //The Flash Status.            
    public UInt32 uCount; // number of times to flash the window            
    public UInt32 dwTimeout; //The rate at which the Window is to be flashed, in milliseconds. If Zero, the function uses the default cursor blink rate.        
}         

[DllImport("user32.dll")]        
[return: MarshalAs(UnmanagedType.Bool)]        
private static extern bool FlashWindowEx(ref FLASHWINFO pwfi);         



public static void FlashWindow(this Window win, UInt32 count = UInt32.MaxValue)        
{            
    //Don't flash if the window is active            
    if (win.IsActive) return;             
    WindowInteropHelper h = new WindowInteropHelper(win);             
    FLASHWINFO info = new FLASHWINFO 
    {                                        
        hwnd = h.Handle,                                        
        dwFlags = FLASHW_ALL | FLASHW_TIMER,                                        
        uCount = count,                                        
        dwTimeout = 0                                    
    };             

    info.cbSize = Convert.ToUInt32(Marshal.SizeOf(info));            
    FlashWindowEx(ref info);        
} 

public static void StopFlashingWindow(this Window win)        
{            
    WindowInteropHelper h = new WindowInteropHelper(win);             
    FLASHWINFO info = new FLASHWINFO();            
    info.hwnd = h.Handle;            
    info.cbSize = Convert.ToUInt32(Marshal.SizeOf(info));            
    info.dwFlags = FLASHW_STOP;            
    info.uCount = UInt32.MaxValue;            
    info.dwTimeout = 0;             
    FlashWindowEx(ref info);        
}

Visit http://www.jarloo.com/flashing-a-wpf-window/ for the complete source.

Pretty interesting scenario. I would have thought it would be something simple. I'll have bookmark this question in the event I ever have to do something similar :)

Answer 3

Scott's example is much simpler... thank you Scott!

https://scottstoecker.wordpress.com/2010/10/08/creating-a-flashing-taskbar-icon-using-flashwindow-with-xaml/

using System.Windows.Interop;
using System.Runtime.InteropServices;

[DllImport("user32")] public static extern int FlashWindow(IntPtr hwnd, bool bInvert);

WindowInteropHelper wih = new WindowInteropHelper(ThisWindow); 
FlashWindow(wih.Handle, true);

Answer 4

Better to use the feature of Windows 7 that is designed for this purpose - taskbar overlay icons. http://10rem.net/blog/2009/12/09/overlaying-icons-on-the-windows-7-taskbar-with-wpf-4 is one of the many places you can see how to do it.

If the attention is needed as part of a long running process, I'd use a taskbar progress bar overlay (also easy to do in WPF) and change its state from Normal to Paused or Error which display as yellow and red respectively. That will get the user's attention.