.NET 6 Preview 4 Blazor - inheriting RouteView causes runtime exception

[Jackwar]

Describe the bug

Inheriting RouteView in a class and replacing RouteView with the inherited class in App.razor causes a runtime exception on startup when using AOT. The error claims that the parameter 'RouteData' is not public.

This scenario still works using the interpreter instead of AOT.

To Reproduce

Inherit RouteView in a class.
public class TestRouteView : RouteView {}

Replace RouteView in App.razor with the custom class.
<Found Context="routeData"> <TestRouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)" /> </Found>

Compile Blazor for AOT. Run the compiled app to cause a runtime exception.

A repo to reproduce is here.

Exceptions (if any)

crit: Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100]
Unhandled exception rendering component: The type 'RouteViewAOTTest.TestRouteView' declares a parameter matching the name 'RouteData' that is not public. Parameters must be public.
System.InvalidOperationException: The type 'RouteViewAOTTest.TestRouteView' declares a parameter matching the name 'RouteData' that is not public. Parameters must be public.

Further technical details

• ASP.NET Core 6 Preview 4
• Include the output of dotnet --info

.NET SDK (reflecting any global.json):
Version: 6.0.100-preview.4.21255.9
Commit: 950e4949a7

Runtime Environment:
OS Name: Windows
OS Version: 10.0.19042
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\6.0.100-preview.4.21255.9\

Host (useful for support):
Version: 6.0.0-preview.4.21253.7
Commit: bfd6048a60

.NET SDKs installed:
3.1.202 [C:\Program Files\dotnet\sdk]
3.1.404 [C:\Program Files\dotnet\sdk]
5.0.201 [C:\Program Files\dotnet\sdk]
5.0.203 [C:\Program Files\dotnet\sdk]
6.0.100-preview.4.21255.9 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.All 2.1.28 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.1.28 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.10 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.0-preview.4.21253.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.1.28 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.10 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.0-preview.4.21253.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.1.10 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.0-preview.4.21254.5 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

To install additional .NET runtimes or SDKs:
https://aka.ms/dotnet-download

• The IDE (VS / VS Code/ VS4Mac) you're running on, and its version

Microsoft Visual Studio Community 2019
Version 16.9.6

• Browsers Tested On
  Google Chrome 91.0.4472.77
  Firefox 88.0.1
  Microsoft Edge 90.0.818.66

[pranavkm]

Thanks for the issue report @Jackwar. This looks like a result of the trimming changes we've been making as part of .NET 6. We'll look at addressing it in an upcoming release, but in the meanwhile you could workaround this by accessing the property setter in your derived component:

public class TestRouteView : RouteView
{
+    public TestRouteView()
+    {
+        RouteData = null;
+    }
}

[Jackwar]

Thanks, the work around worked. I found I also needed to access DefaultLayout.

public class TestRouteView : RouteView
{
+    public TestRouteView()
+    {
+        RouteData = null;
+        DefaultLayout = null;
+    }
}

[vitek-karas]

This is a bug in mono/linker. dotnet/linker#2059

[mkArtakMSFT]

Thanks for contacting us.
Looks like the underlying linker issue is now resolved and will be released in a future version of 6.0 previews.