Update to SDK 2.2.100 throws "An item with the same key has already been added. Key: .wasm"

I updated my Blazor project from 2.2.100-preview3-009430 to 2.2.100 release. I now get the following exception:

System.ArgumentException : An item with the same key has already been added. Key: .wasm
Stack Trace:
   at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)
   at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
   at Microsoft.AspNetCore.Builder.BlazorApplicationBuilderExtensions.CreateContentTypeProvider(Boolean enableDebugging)
   at Microsoft.AspNetCore.Builder.BlazorApplicationBuilderExtensions.UseBlazor(IApplicationBuilder app, BlazorOptions options)
   at Microsoft.AspNetCore.Builder.ServerSideBlazorApplicationBuilderExtensions.UseServerSideBlazor[TStartup](IApplicationBuilder builder)
   at OpenGraphTilemaker.Web.Server.Startup.Configure(IApplicationBuilder app, IHostingEnvironment env) in C:\Users\flynn\Projects\OpenGraphTilemaker\src\OpenGraphTilemaker.Web.Server\Startup.cs:line 36
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Hosting.ConventionBasedStartup.Configure(IApplicationBuilder app)
   at Microsoft.AspNetCore.HostFilteringStartupFilter.<>c__DisplayClass0_0.<Configure>b__0(IApplicationBuilder app)
   at Microsoft.AspNetCore.Hosting.Internal.AutoRequestServicesStartupFilter.<>c__DisplayClass0_0.<Configure>b__0(IApplicationBuilder builder)
   at Microsoft.AspNetCore.Hosting.Internal.WebHost.BuildApplication()
   at Microsoft.AspNetCore.Hosting.Internal.WebHost.StartAsync(CancellationToken cancellationToken)
   at Microsoft.AspNetCore.TestHost.TestServer..ctor(IWebHostBuilder builder, IFeatureCollection featureCollection)
   at Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory`1.CreateServer(IWebHostBuilder builder)
   at Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory`1.EnsureServer()
   at Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory`1.CreateDefaultClient(DelegatingHandler[] handlers)
   at Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory`1.CreateClient(WebApplicationFactoryClientOptions options)
   at OpenGraphTilemaker.Web.Client.Tests.FunctionalTests.Get_EndpointsReturnSuccessAndCorrectContentType(String url) in C:\Users\flynn\Projects\OpenGraphTilemaker\tests\OpenGraphTilemaker.Web.Client.Tests\FunctionalTests.cs:line 25
--- End of stack trace from previous location where exception was thrown ---

The line app.UseServerSideBlazor<Client.Startup>(); seems to be the reason.

Any suggestions?

[danroth27]

Thanks everyone for reporting this issue! I apologize for the inconvenience.

To workaround this issue you will need to have your Blazor projects continue to target .NET Core 2.1 (netcoreapp2.1). We aren’t planning to patch this issue because there is a workaround and we are currently focused on getting Razor Components into .NET Core 3.0. This issue will be fixed once we release the first public preview of Razor Components early next year.

[isaacrlevin]

@danroth27 So to summarize, there is currently no support for Blazor on .NET Core 2.2?