Вывести окно вперед на Windows 8

вот решение, которое работает в моих приложениях. (возможно, необходимо вызвать это с помощью Dispatcher.CurrentDispatcher.BeginInvoke)

public static void ShowAndActivate(this Window window)
{
  if (window == null) {
    return;
  }
  var hwnd = new WindowInteropHelper(window).Handle;
  ActivateWindowHandle(hwnd);
}

/// <summary>
/// Activates and sets focus to the Window Object
/// </summary>
public static void ActivateWindowHandle(IntPtr hWnd)
{
  var threadId1 = GetWindowThreadProcessId(GetForegroundWindow(), IntPtr.Zero);
  var threadId2 = GetWindowThreadProcessId(hWnd, IntPtr.Zero);

  if (threadId1 != threadId2) {
    AttachThreadInput(threadId1, threadId2, 1);
    SetForegroundWindow(hWnd);
    AttachThreadInput(threadId1, threadId2, 0);
  } else {
    SetForegroundWindow(hWnd);
  }

  if (IsIconic(hWnd)) {
    ShowWindowAsync(hWnd, ShowWindowCommands.Restore);
  } else {
    ShowWindowAsync(hWnd, ShowWindowCommands.Show);
  }
}

[DllImport("user32.dll")]
public static extern bool IsIconic(IntPtr hWnd);

[DllImport("user32.dll")]
public static extern IntPtr GetForegroundWindow();

[DllImport("user32.dll")]
public static extern IntPtr AttachThreadInput(IntPtr idAttach, IntPtr idAttachTo, int fAttach);

[DllImport("user32.dll")]
public static extern IntPtr GetWindowThreadProcessId(IntPtr hWnd, IntPtr ProcessId);

[DllImport("user32.dll")]
public static extern bool ShowWindowAsync(IntPtr hWnd, ShowWindowCommands cmdShow);

[DllImport("user32.dll")]
public static extern int SetForegroundWindow(IntPtr hWnd);

public enum ShowWindowCommands : int
{
  /// <summary>
  /// Hides the window and activates another window.
  /// </summary>
  Hide = 0,
  /// <summary>
  /// Activates and displays a window. If the window is minimized or 
  /// maximized, the system restores it to its original size and position.
  /// An application should specify this flag when displaying the window 
  /// for the first time.
  /// </summary>
  Normal = 1,
  /// <summary>
  /// Activates the window and displays it as a minimized window.
  /// </summary>
  ShowMinimized = 2,
  /// <summary>
  /// Maximizes the specified window.
  /// </summary>
  Maximize = 3, // is this the right value?
  /// <summary>
  /// Activates the window and displays it as a maximized window.
  /// </summary>       
  ShowMaximized = 3,
  /// <summary>
  /// Displays a window in its most recent size and position. This value 
  /// is similar to <see cref="Win32.ShowWindowCommand.Normal"/>, except 
  /// the window is not activated.
  /// </summary>
  ShowNoActivate = 4,
  /// <summary>
  /// Activates the window and displays it in its current size and position. 
  /// </summary>
  Show = 5,
  /// <summary>
  /// Minimizes the specified window and activates the next top-level 
  /// window in the Z order.
  /// </summary>
  Minimize = 6,
  /// <summary>
  /// Displays the window as a minimized window. This value is similar to
  /// <see cref="Win32.ShowWindowCommand.ShowMinimized"/>, except the 
  /// window is not activated.
  /// </summary>
  ShowMinNoActive = 7,
  /// <summary>
  /// Displays the window in its current size and position. This value is 
  /// similar to <see cref="Win32.ShowWindowCommand.Show"/>, except the 
  /// window is not activated.
  /// </summary>
  ShowNA = 8,
  /// <summary>
  /// Activates and displays the window. If the window is minimized or 
  /// maximized, the system restores it to its original size and position. 
  /// An application should specify this flag when restoring a minimized window.
  /// </summary>
  Restore = 9,
  /// <summary>
  /// Sets the show state based on the SW_* value specified in the 
  /// STARTUPINFO structure passed to the CreateProcess function by the 
  /// program that started the application.
  /// </summary>
  ShowDefault = 10,
  /// <summary>
  ///  <b>Windows 2000/XP:</b> Minimizes a window, even if the thread 
  /// that owns the window is not responding. This flag should only be 
  /// used when minimizing windows from a different thread.
  /// </summary>
  ForceMinimize = 11
}

Вы пробовали их сочетание?

Window.Activate();
Window.Topmost = true;
Window.Topmost = false; 
Window.Focus();         

Это более обходное решение, но это очень помогло мне, когда окно застряло за чем-то другим.

Это также помогло мне, когда я получил цепочку ShowDialog() потому что иногда.NET имеет странное поведение, когда речь заходит о нескольких ShowDialog()