graphicsDevice.PlatformDispose throws System.NullReferenceException

[EnemyArea]

After upgrade to monogame 3.7, I've got an NullReferenceException on calling graphicsDevice.Dispose, if monogame is used in a wpf application. Thats because, there is no _swapChain. The line is the first line @ PlatformDispose

"if (_swapChain.IsFullScreen)" <- Here should be checked whether _swapChain is not null

Before 3.7 that error not exists. I have testet on the latest dev branch on Windows 10 Prof.

What version of MonoGame does the bug occur on:

• MonoGame 3.7

What operating system are you using:

• Windows 10

What MonoGame platform are you using:

• WindowsDX

[craftworkgames]

I ran into the same issue.

The problem should be reproduceable in my MonoGame.WpfCore project.

The exception occurs when the application is shutting down and the GraphicsDevice is disposed on line 18. Although it doesn't seem to happen all the time (maybe some sort of race condition or maybe the debugger is detached before it happens, I'm not sure).

Here's the stack trace I got:

   at SharpDX.DXGI.SwapChain.GetFullscreenState(RawBool& fullscreenRef, Output& targetOut)
   at SharpDX.DXGI.SwapChain.get_IsFullScreen()
   at Microsoft.Xna.Framework.Graphics.GraphicsDevice.PlatformDispose()
   at Microsoft.Xna.Framework.Graphics.GraphicsDevice.Dispose(Boolean disposing)
   at Microsoft.Xna.Framework.Graphics.GraphicsDevice.Dispose()
   at SpriteFactory.MonoGameControls.MonoGameGraphicsDeviceService.Dispose()
   at SpriteFactory.MonoGameControls.MonoGameContentControl.CleanUp()
   at SpriteFactory.MonoGameControls.MonoGameContentControl.Finalize()

The problem is quite clear after stepping into the code. In the PlatformDispose method the _swapChain variable is used to change the fullscreen state without checking it for null.

      if (this._swapChain.IsFullScreen)
        this._swapChain.SetFullscreenState((RawBool) false, (Output) null);

But in other parts of the code it is consistently checked for null. For example in the CreateSizeDependentResources method a very similar bit of code exists.

          if (this._swapChain != null)
          {
            flag = this._swapChain.IsFullScreen;
            this._swapChain.SetFullscreenState((RawBool) false, (Output) null);
            this._swapChain.Dispose();
          }