OpenCapturePicker

private async Task OpenCapturePicker()
{
    var picker = new GraphicsCapturePicker();
    var handle = new WindowInteropHelper(this).Handle;

    var interop = (IInitializeWithWindow)(object)picker;
    interop.Initialize(handle);

    await picker.PickSingleItemAsync();
}

[ComImport, Guid("3E68D4BD-7135-4D10-8018-9FB6D9F33FA1"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
private interface IInitializeWithWindow
{
    void Initialize(IntPtr hwnd);
}