WPF minimized window setting to restore

Question

I'm getting some very odd behaviour with a WPF window that I am able to recreate with a basic application. When I minimize my window from a maximized state, then restore my window it does not return maximized. I've implemented code to try and counter this, but the window still returns to a WindowState.Normal.

An important thing to note about this is the this only happen when I am running the application stand-alone. If I run in debug mode in visual studio everything works as expected. Also, this behaviour occurs on multiple boxes, not just my own.

Steps to reproduce with code below:

1. double-click WpfApplication1.exe
2. ensure application is maximized
3. click the minimize button in the top right

4. click the application in the taskbar

   Expected Result: application window returns to a maximized state

   Actual Result: application window is in restored state, with WindowState = WindowState.Normal

Here is the XAML code for the demo window.

<Window x:Class="WpfApplication1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525"
    WindowState="Maximized"
    Activated="MainWindow_OnActivated"
    StateChanged="MainWindow_OnStateChanged">
    <Grid>

    </Grid>
</Window>

and the code-behind:

public partial class MainWindow : Window
{
  private WindowState _lastWindowState;
  private bool _activating;

  public MainWindow()
  {
    InitializeComponent();

    _lastWindowState = WindowState.Normal;
  }

  private void MainWindow_OnActivated(object sender, EventArgs e)
  {

    if (WindowState == WindowState.Minimized)
    {
      WindowState = _lastWindowState;
    }

  }

  private void MainWindow_OnStateChanged(object sender, EventArgs e)
  {
    if (WindowState != WindowState.Minimized)
    {
      _lastWindowState = WindowState;
    }
  }
}

In my real application I placed logging code before and after the WindowState set in the OnActivated function and in the StateChanged function. When activating from minimized I get the following:

OnActivated 1  - _lastWindowState: Maximized
OnStateChanged - _lastWindowState: Maximized
OnActivated 2  - _lastWindowState: Maximized
OnStateChanged - _lastWindowState: Normal

Finally, in case this helps, this is the Environment.StackTrace in the last StateChanged call that happens:

at System.Environment.GetStackTrace(Exception e, Boolean needFileInfo)
   at System.Environment.get_StackTrace()
   at MapViewer.MainWindow.MainWindow_OnStateChanged(Object sender, EventArgs e) in c:\APP\MainWindow.xaml.cs:line 994
   at System.Windows.Window.OnStateChanged(EventArgs e)
   at System.Windows.Window.WmSizeChanged(IntPtr wParam)
   at System.Windows.Window.WindowFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at System.Windows.Interop.HwndSource.PublicHooksFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)
   at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
   at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at MS.Win32.UnsafeNativeMethods.CallWindowProc(IntPtr wndProc, IntPtr hWnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at MS.Win32.HwndSubclass.DefWndProcWrapper(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at MS.Win32.UnsafeNativeMethods.CallWindowProc(IntPtr wndProc, IntPtr hWnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at MS.Win32.UnsafeNativeMethods.CallWindowProc(IntPtr wndProc, IntPtr hWnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at MS.Win32.HwndSubclass.DefWndProcWrapper(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at MS.Win32.UnsafeNativeMethods.CallWindowProc(IntPtr wndProc, IntPtr hWnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
   at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
   at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame)
   at System.Windows.Threading.Dispatcher.Run()
   at System.Windows.Application.RunDispatcher(Object ignore)
   at System.Windows.Application.RunInternal(Window window)
   at System.Windows.Application.Run(Window window)
   at System.Windows.Application.Run()
   at MapViewer.App.Main() in c:\Projects\APP\obj\x86\Debug\App.g.cs:line 0