Blazor Wasm 6.0.0 Preview 2: Launching via IIS Express no longer works.

[makotech222]

Describe the bug

In upgrading a blazor wasm app from .net 5.0 to .net 6.0 preview 1 + preview 2, I can no longer launch the application using the IIS Express launch profile in Visual studio 16.10 Preview 1. The specific error when launching into browser is:

HTTP Error 500.33 - ANCM Request Handler Load Failure
Could not find the assembly 'aspnetcorev2_inprocess.dll' referenced for the in-process application. Please confirm the Microsoft.AspNetCore.Server.IIS or Microsoft.AspNetCore.App is referenced in your application.

In addition, creating a brand new wasm app using .net 6 preview 2 has the same issue.

To Reproduce

Using Visual Studio 16.10 Preview 1, create a new blazor wasm app, using .net 6 preview 2. Make sure ASP NET Core hosting is turned off. Run the application using the default IIS Express launch profile.

Further technical details

• .net 6.0 Preview 2
• .NET SDK (reflecting any global.json):
  Version: 6.0.100-preview.2.21155.3
  Commit: 1a9103db2d

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.2.21155.3\

Host (useful for support):
Version: 6.0.0-preview.2.21154.6
Commit: 3eaf1f316b

.NET SDKs installed:
5.0.100 [C:\Program Files\dotnet\sdk]
5.0.102 [C:\Program Files\dotnet\sdk]
5.0.200-preview.21077.7 [C:\Program Files\dotnet\sdk]
6.0.100-preview.2.21155.3 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.All 2.1.23 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.All 2.1.24 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.1.23 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 2.1.24 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.0-preview.2.21154.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.1.23 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.1.24 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.2 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.0-preview.2.21154.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.1.9 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 3.1.11 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 5.0.2 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.0-preview.2.21154.2 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

• Visual Studio 16.10 Preview 1.

[pranavkm]

I imagine this isn't blazor specific. Are there docs for using preview builds of the SDK + IIS Express?

[pranavkm]

@makotech222 do you also see this issue if you create a brand new MVC or Razor Pages app?

[danroth27]

I'm able to repro this with .NET 6 Preview 2 and VS 16.10 Preview 1. It only repros with the standalone Blazor WebAssembly template. I get the same error mentioned above in the event logs: "Could not find the assembly 'aspnetcorev2_inprocess.dll' referenced for the in-process application. Please confirm the Microsoft.AspNetCore.Server.IIS or Microsoft.AspNetCore.App is referenced in your application."

[makotech222]

@makotech222 do you also see this issue if you create a brand new MVC or Razor Pages app?

Those app types work fine, as normal. Only blazor wasm app is affected.

Thanks for contacting us.
We're moving this issue to the Next sprint planning milestone for future evaluation / consideration. We will evaluate the request when we are planning the work for the next milestone. To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.