Feature 'Razor TagHelperProvider Feature' is currently unavailable due to an internal error

[Sella-GH]

Version Used:
Visual Studio 17.14 Preview 2.0

Steps to Reproduce:

1. Create a new ASP.NET Core Web API
2. Let "Use Controllers" checked
3. Experience internal error

Minimal Repro:

TagHelperProviderMinimalRepro.zip

Expected Behavior:
No error to be shown.

Actual Behavior:
Error shown, Stack Trace:

StreamJsonRpc.RemoteInvocationException: Method not found: 'Void Microsoft.AspNetCore.Razor.Language.TagHelperDescriptorProviderContext.set_ExcludeHidden(Boolean)'.
   at StreamJsonRpc.JsonRpc.<InvokeCoreAsync>d__156`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Threading.Tasks.ValueTask`1.get_Result()
   at Microsoft.CodeAnalysis.Remote.BrokeredServiceConnection`1.<TryInvokeAsync>d__18`1.MoveNext()
RPC server exception:
System.MissingMethodException: Method not found: 'Void Microsoft.AspNetCore.Razor.Language.TagHelperDescriptorProviderContext.set_ExcludeHidden(Boolean)'.
      at Microsoft.CodeAnalysis.ProjectExtensions.GetTagHelpersAsync(Project project, RazorProjectEngine projectEngine, ITelemetryReporter telemetryReporter, CancellationToken cancellationToken)
      at System.Runtime.CompilerServices.AsyncMethodBuilderCore.Start[TStateMachine](TStateMachine& stateMachine)
      at Microsoft.CodeAnalysis.ProjectExtensions.GetTagHelpersAsync(Project project, RazorProjectEngine projectEngine, ITelemetryReporter telemetryReporter, CancellationToken cancellationToken)
      at Microsoft.CodeAnalysis.Remote.Razor.RemoteTagHelperResolver.GetTagHelpersAsync(Project workspaceProject, RazorConfiguration configuration, CancellationToken cancellationToken)
      at Microsoft.CodeAnalysis.Remote.Razor.RemoteTagHelperProviderService.GetTagHelpersDeltaCoreAsync(Solution solution, ProjectSnapshotHandle projectHandle, Int32 lastResultId, CancellationToken cancellationToken)
      at Microsoft.CodeAnalysis.Remote.RemoteWorkspace.<>c__DisplayClass7_0`1.<<RunWithSolutionAsync>g__ProcessSolutionAsync|1>d.MoveNext()
   --- End of stack trace from previous location ---
      at Microsoft.CodeAnalysis.Remote.RemoteWorkspace.RunWithSolutionAsync[T](AssetProvider assetProvider, Checksum solutionChecksum, Boolean updatePrimaryBranch, Func`2 implementation, CancellationToken cancellationToken)
      at Microsoft.CodeAnalysis.Remote.RemoteWorkspace.RunWithSolutionAsync[T](AssetProvider assetProvider, Checksum solutionChecksum, Boolean updatePrimaryBranch, Func`2 implementation, CancellationToken cancellationToken)
      at Microsoft.CodeAnalysis.Remote.RemoteWorkspaceManager.RunServiceAsync[T](ServiceBrokerClient client, Checksum solutionChecksum, Func`2 implementation, CancellationToken cancellationToken)

[phil-allen-msft]

We're sorry you are running into this. We believe this is fixed with dotnet/roslyn#77720