Why some of the answers on this page are wrong!
Essentially:
- The window should not grab the focus away from any other window when it activates;
- The window should not activate its parent when it is shown;
- The window should be compatible with Citrix.
MVVM Solution
This code is 100% compatible with Citrix (no blank areas of the screen). It is tested with both normal WPF and DevExpress.
This answer is intended for any use case where we want a small notification window that is always in front of other windows (if the user selects this in the preferences).
If this answer seems more complex than the others, it's because it is robust, enterprise level code. Some of the other answers on this page are simple, but do not actually work.
XAML - Attached Property
Add this attached property to any UserControl
within the window. The attached property will:
- Wait until the
Loaded
event is fired (otherwise it cannot look up the visual tree to find the parent window).
- Add an event handler that ensures that the window is visible or not.
At any point, you can set the window to be in front or not, by flipping the value of the attached property.
<UserControl x:Class="..."
...
attachedProperties:EnsureWindowInForeground.EnsureWindowInForeground=
"{Binding EnsureWindowInForeground, Mode=OneWay}">
C# - Helper Method
public static class HideAndShowWindowHelper
{
/// <summary>
/// Intent: Ensure that small notification window is on top of other windows.
/// </summary>
/// <param name="window"></param>
public static void ShiftWindowIntoForeground(Window window)
{
try
{
// Prevent the window from grabbing focus away from other windows the first time is created.
window.ShowActivated = false;
// Do not use .Show() and .Hide() - not compatible with Citrix!
if (window.Visibility != Visibility.Visible)
{
window.Visibility = Visibility.Visible;
}
// We can't allow the window to be maximized, as there is no de-maximize button!
if (window.WindowState == WindowState.Maximized)
{
window.WindowState = WindowState.Normal;
}
window.Topmost = true;
}
catch (Exception)
{
// Gulp. Avoids "Cannot set visibility while window is closing".
}
}
/// <summary>
/// Intent: Ensure that small notification window can be hidden by other windows.
/// </summary>
/// <param name="window"></param>
public static void ShiftWindowIntoBackground(Window window)
{
try
{
// Prevent the window from grabbing focus away from other windows the first time is created.
window.ShowActivated = false;
// Do not use .Show() and .Hide() - not compatible with Citrix!
if (window.Visibility != Visibility.Collapsed)
{
window.Visibility = Visibility.Collapsed;
}
// We can't allow the window to be maximized, as there is no de-maximize button!
if (window.WindowState == WindowState.Maximized)
{
window.WindowState = WindowState.Normal;
}
window.Topmost = false;
}
catch (Exception)
{
// Gulp. Avoids "Cannot set visibility while window is closing".
}
}
}
Usage
In order to use this, you need to create the window in your ViewModel:
private ToastView _toastViewWindow;
private void ShowWindow()
{
if (_toastViewWindow == null)
{
_toastViewWindow = new ToastView();
_dialogService.Show<ToastView>(this, this, _toastViewWindow, true);
}
ShiftWindowOntoScreenHelper.ShiftWindowOntoScreen(_toastViewWindow);
HideAndShowWindowHelper.ShiftWindowIntoForeground(_toastViewWindow);
}
private void HideWindow()
{
if (_toastViewWindow != null)
{
HideAndShowWindowHelper.ShiftWindowIntoBackground(_toastViewWindow);
}
}
Additional links
For tips on how ensure that a notification window always shifts back onto the visible screen, see my answer: In WPF, how to shift a window onto the screen if it is off the screen?.