Compiler warning and runtime exception on UWP Release

The library works fine on Debug UWP builds but gives the compiler warnings for each of the unsupported windows p/invoke calls when built in Release. For example:

MCG : warning MCG0007: Unresolved P/Invoke method 'user32.dll!CloseClipboard' for method 'System.Boolean WindowsClipboard.CloseClipboard()'.
 Calling this method would throw exception at runtime.
 Please make sure the P/Invoke either points to a Windows API allowed in UWP applications, or a native DLL that is part of the package. 
If for some reason your P/Invoke does not satisfy those requirements, please use [DllImport(ExactSpelling=true) to indicate that you understand the implications of using non-UWP APIs		

At runtime the promised exception is thrown when trying to cut, copy or paste.

This is using a UWP with a minimum target version of 10.0.16299. I don’t see the clipboard windows calls listed in the available APIs: https://docs.microsoft.com/en-us/uwp/win32-and-com/win32-and-com-for-uwp-apps

I will attempt a fix for my own app that uses the UWP Clipboard https://docs.microsoft.com/en-us/windows/uwp/app-to-app/copy-and-paste

If that works I’ll make a PR for this library.

[SimonCropp]

can u submit a failing PR with that code?

[HaikuJock]

I think there’s definitely something weird with my setup which I’m going to look into further.

I tried copying your test code by getting and setting on a thread and it worked fine.

I then tried repeatedly firing the get and set on new threads:

        public MainPage()
        {
            InitializeComponent();
            var thread1 = new Thread(TestClipboard);
            thread1.Start();
        }

        void TestClipboard()
        {
            var random = new Random();
            while (true)
            {
                var thread = new Thread(OutputClipboardText);
                thread.Start();
                Thread.Sleep(random.Next(1, 100) * 10);
            }
        }

        async void OutputClipboardText()
        {
            await TextCopy.Clipboard.SetText("AAA");
            var text = await TextCopy.Clipboard.GetText();
            Debug.WriteLine("Clipboard");
            if (text == null)
            {
                Debug.WriteLine("NULL");
            }
            else
            {
                Debug.WriteLine(text);
            }
        }

I found two things from this:

1. Sometimes the result of GetText was null
2. An unhandled exception was occasionally thrown with error code CLIPBRD_E_CANT_OPEN. I vaguely seeing code where you handled this for the .NET framework version. https://stackoverflow.com/questions/68666/clipbrd-e-cant-open-error-when-setting-the-clipboard-from-net