Setting Content on ContentControl crashes trimmed app

[styris-ame]

Describe the bug

After publishing a self contained, trimmed single file WinUI 3 executable, most things work normally. However, if you try to set the Content property on a ContentControl it will throw an exception:

[InvalidCastException] No such interface supported

int RoutedEventHandler.Do_Abi_Invoke(thisPtr, sender, e) >
RoutedEventHandler EventState.GetEventInvoke(sender, e) >
void PageViewer.OnApplyTemplate(sender, args) in PageViewer.cs:69 >
void PageViewer.SetCurrentPage(index) in PageViewer.cs:278 >
void ContentControl.set_Content(value) >
void IContentControlMethods.set_Content(_obj, value) >
void ExceptionHelpers.ThrowExceptionForHR(hr)

I assume the failure is due to IContentControlMethods getting trimmed.

Steps to reproduce the bug

Create a self-contained unpackaged WinUI app, and publish as trimmed and single file.

NuGet package version

Microsoft.WindowsAppSDK 1.6.250205002

1.7.250208002-preview1 has a similar error too:

[InvalidCastException] Specified cast is not valid.

int RoutedEventHandler.Do_Abi_Invoke(thisPtr, sender, e) >
RoutedEventHandler EventState.GetEventInvoke(sender, e) >
void PageViewer.OnApplyTemplate(sender, args) in PageViewer.cs:69 >
void PageViewer.SetCurrentPage(index) in PageViewer.cs:278 >
void ContentControl.set_Content(value) >
void IContentControlMethods.set_Content(_obj, value) >
void ExceptionHelpers.ThrowExceptionForHR(hr)

Windows version

Windows 11 24H2

Workaround

As a workaround, adding the following to the project csproj file solves the problem at the cost of adding ~7MB to the executable:

<ItemGroup>
    <TrimmerRootAssembly Include="Microsoft.WinUI"/>
</ItemGroup>

[snigdha011997]

Hi @styris-ame , can you please us by providing the repro project that has caused the above issue, it will help us investigate and help you further.

[microsoft-github-policy-service]

This issue has been automatically marked as stale because it has been marked as requiring author feedback but has not had any activity for 7 days. It will be closed if no further activity occurs within 7 days of this comment.