Get user attention without stealing focus

Option A: You need to use FlashWindowEx from the windows API. This isn't available in .NET, so you need to use PInvoke.

Option B: Use a balloon tip from the system tray. This is built into .NET, but requires that your application use a notification icon, which you might not want. More details here: http://msdn.microsoft.com/en-us/library/system.windows.forms.notifyicon.showballoontip.aspx

Here is the example for how to use Option A:

pInvoke.net has the best example: http://pinvoke.net/default.aspx/user32.FlashWindowEx

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

User-Defined Types:

[StructLayout(LayoutKind.Sequential)]
public struct FLASHWINFO
{
    public UInt32 cbSize;
    public IntPtr hwnd;
    public UInt32 dwFlags;
    public UInt32 uCount;
    public UInt32 dwTimeout;
}

Notes:

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

Tips & Tricks:

Please add some!

Sample Code:

/// <summary>
/// Flashes a window
/// </summary>
/// <param name="hWnd">The handle to the window to flash</param>
/// <returns>whether or not the window needed flashing</returns>
public static bool FlashWindowEx(IntPtr hWnd)
{
    FLASHWINFO fInfo = new FLASHWINFO();

    fInfo.cbSize = Convert.ToUInt32(Marshal.SizeOf(fInfo));
    fInfo.hwnd = hWnd;
    fInfo.dwFlags = FLASHW_ALL;
    fInfo.uCount = UInt32.MaxValue;
    fInfo.dwTimeout = 0;

    return FlashWindowEx(ref fInfo);
}

...

/// Minor adjust to the code above
/// <summary>
/// Flashes a window until the window comes to the foreground
/// Receives the form that will flash
/// </summary>
/// <param name="hWnd">The handle to the window to flash</param>
/// <returns>whether or not the window needed flashing</returns>
public static bool FlashWindowEx(Form frm)
{
        IntPtr hWnd = frm.Handle;
        FLASHWINFO fInfo = new FLASHWINFO();

        fInfo.cbSize = Convert.ToUInt32(Marshal.SizeOf(fInfo));
        fInfo.hwnd = hWnd;
        fInfo.dwFlags = FLASHW_ALL | FLASHW_TIMERNOFG;
        fInfo.uCount = UInt32.MaxValue;
        fInfo.dwTimeout = 0;

        return FlashWindowEx(ref fInfo);
}

Here is the official Microsoft example: http://msdn.microsoft.com/en-us/library/ms679347(v=vs.85).aspx

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

    [StructLayout(LayoutKind.Sequential)]
    public struct FLASHWINFO
    {
        /// <summary>
        /// The size of the structure in bytes.
        /// </summary>
        public uint cbSize;
        /// <summary>
        /// A Handle to the Window to be Flashed. The window can be either opened or minimized.
        /// </summary>
        public IntPtr hwnd;
        /// <summary>
        /// The Flash Status.
        /// </summary>
        public FlashWindowFlags dwFlags; //uint
        /// <summary>
        /// The number of times to Flash the window.
        /// </summary>
        public uint uCount;
        /// <summary>
        /// The rate at which the Window is to be flashed, in milliseconds. If Zero, the function uses the default cursor blink rate.
        /// </summary>
        public uint dwTimeout;
    }


    public enum FlashWindowFlags : uint
    {
        /// <summary>
        /// Stop flashing. The system restores the window to its original state.
        /// </summary>
        FLASHW_STOP = 0,

        /// <summary>
        /// Flash the window caption.
        /// </summary>
        FLASHW_CAPTION = 1,

        /// <summary>
        /// Flash the taskbar button.
        /// </summary>
        FLASHW_TRAY = 2,

        /// <summary>
        /// Flash both the window caption and taskbar button.
        /// This is equivalent to setting the FLASHW_CAPTION | FLASHW_TRAY flags.
        /// </summary>
        FLASHW_ALL = 3,

        /// <summary>
        /// Flash continuously, until the FLASHW_STOP flag is set.
        /// </summary>
        FLASHW_TIMER = 4,

        /// <summary>
        /// Flash continuously until the window comes to the foreground.
        /// </summary>
        FLASHW_TIMERNOFG = 12
    }


    public static bool FlashWindow(IntPtr hWnd, 
                                   FlashWindowFlags fOptions, 
                                   uint FlashCount, 
                                   uint FlashRate)
    {
        if(IntPtr.Zero != hWnd)
        {
            FLASHWINFO fi = new FLASHWINFO();
            fi.cbSize = (uint)Marshal.SizeOf(typeof(FLASHWINFO));
            fi.dwFlags = fOptions;
            fi.uCount = FlashCount;
            fi.dwTimeout = FlashRate;
            fi.hwnd = hWnd;

            return FlashWindowEx(ref fi);
        }
        return false;
    }

    public static bool StopFlashingWindow(IntPtr hWnd)
    {
        if(IntPtr.Zero != hWnd)
        {
            FLASHWINFO fi = new FLASHWINFO();
            fi.cbSize = (uint)Marshal.SizeOf(typeof(FLASHWINFO));
            fi.dwFlags = (uint)FlashWindowFlags.FLASHW_STOP;
            fi.hwnd = hWnd;

            return FlashWindowEx(ref fi);
        }
        return false;
    }

In Windows 7, a progress bar on a form is represented in its taskbar button; you might leverage that. There's also got to be a way to simply highlight the taskbar button, like IM programs do when you get a new message.

Tags:

C#

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