After update to Blazor 0.8 library _content missing

[sven5]

Describe the bug

In Blazor library it's impossible to load client side files from "magical" folder _content after update to .NET Core 3.0 Preview 2 and Blazor 0.8.

To Reproduce

Steps to reproduce the behavior:

1. Using this version of ASP.NET Core '3.0.0-preview-19705-0444'
2. Update Blazor library to use the following packages:

<ItemGroup> <PackageReference Include="Microsoft.AspNetCore.Components.Browser" Version="3.0.0-preview-19075-0444" /> <PackageReference Include="Microsoft.AspNetCore.Components.Build" Version="3.0.0-preview-19075-0444" /> </ItemGroup>

Edit: Need to say that my Blazor App runs as a mapped sub-application:

app.Map("/Blazor", branchApp =>
{
	branchApp.UseStaticFiles();
	branchApp.UseRazorComponents<App.Startup>();
});

But this was no issue in 0.7.
This seems to be only an issue with Razor Components (server-side). In client side scenario (Blazor) it's working correctly.

Expected behavior

I expect the folder _content to be accessible and visible through debugging tools in the browser as it was with Blazor 0.7

Screenshots

As you can see in the following screenshot, the folder _content is not available.

Additional context

Add any other context about the problem here.
Include the output of dotnet --info

Host (useful for support):
Version: 3.0.0-preview-27324-5
Commit: 63a01b08e5

.NET Core SDKs installed:
2.1.202 [C:\Program Files\dotnet\sdk]
2.1.503 [C:\Program Files\dotnet\sdk]
2.1.600-preview-009472 [C:\Program Files\dotnet\sdk]
3.0.100-preview-010184 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed:
Microsoft.AspNetCore.All 2.1.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.1.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.0.0-preview-19075-0444 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.1.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.0.0-preview-27324-5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.0.0-preview-27325-3 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

[mkArtakMSFT]

Thanks for contacting us, @sven5.
We don't yet support content files in Razor Components. This is something on our backlog and we plan to address it in the future: #6349

[SQL-MisterMagoo]

@sven5 Until the Microsoft team get this working, I have written a project that brings this functionality back for Razor Components BlazorEmbedLibrary
If you add this to your App, it will embed the static CSS and JS files at runtime into the head of your app using browser blob storage.
You might find it useful as a workaround.