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DebugSettings.EnableFrameRateCounter = true in Desktop causes an AccessViolation

See original GitHub issue

Describe the bug Create a new WinUI Desktop application and set the DebugSettings.EnableFrameRateCounter = true in the application constructor or the OnLaunched and an access violation exception will occur when the application is run.

Exception thrown at 0x7A0D38FC (Microsoft.UI.Xaml.dll) in WinUI_InDesktop.exe: 0xC0000005: Access violation reading location 0x00000000.

Steps to reproduce the bug

In the attached solution, run the WinUiDesktop (Package) application. Note that you will be able to safely step over enabling the frame rate counter but the application will crash shortly after.
For comparision, using the same solution, run the BlankAppUWP (Package). Note that the application will not crash and it will show the framerate counter as expected.

Expected behavior If by chance the DebugSettings.EnableFrameRateCounter setting cannot be used with Desktop applications, then a non-fatal exception message should be thrown. If this feature is supported in Desktop applications then it has a bug.

Screenshots

Version Info .Net5.0 Preview 6

NuGet package version: <PackageReference Include="Microsoft.WinUI" Version="3.0.0-preview1.200515.3" />

Note that I have been making WinUI work with Preview 6 by adding this additional direct package reference, a trick I learned from Scott Jones. Although I have been able to accomplish quite a bit of Window related work without any crashes, it was worth mentioning.

<PackageReference Include="Microsoft.Windows.CsWinRT" Version="0.1.0-prerelease.200623.5" />

Windows 10 version	Saw the problem?
Insider Build (xxxxx)
May 2020 Update (19041)	Yes
November 2019 Update (18363)
May 2019 Update (18362)
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