Sample application build error

I try to build and run the sample application

I use VS2019, build and receive the error:

Startup.cs(27,38,27,51): error CS0411: The type arguments for method 'SignalRDependencyInjectionExtensions.AddHubOptions(ISignalRServerBuilder, Action<HubOptions>)' cannot be inferred from the usage. Try specifying the type arguments explicitly.

How to fix it?

Please make sure you have latest .NET Core 3.0 Preview 7 installed. You need also latest VS2019 Preview:

Ok, thanx, I see.
It is for VS2019+NET Core 3 only.
As I understand the VS2017+NET Core 2.2 does not work?

No. To run Blazor applications you need latest .NET Core 3.0 and VS 2019 Preview

By the way: may be need to add note about using VS2019+NET Core 3 to

and to git page too