Obsolete WebHostBuilder

[Tratcher]

WebHostBuilder was replaced by HostBuilder in 3.0. In 5.0 we should consider obsoleting the old one.

[analogrelay]

To clarify even more, the idea here is to obsolete the types and public APIs on:

• WebHost
• WebHostBuilder
• Add an "obsolete" banner to https://docs.microsoft.com/en-us/aspnet/core/fundamentals/host/web-host?view=aspnetcore-3.1

The obsolete message should include an aka.ms link that points to https://docs.microsoft.com/en-us/aspnet/core/fundamentals/host/generic-host?view=aspnetcore-3.1#settings-for-web-apps

[davidfowl]

We shouldn’t do this until we resolve the remaining gaps that people complain about:

• Passing extra state to the startup class (for e.g)

[Tratcher]

• Passing extra state to the startup class

Related issue: #19809

[davidfowl]

Also the IStartup replacement.

[BrennanConroy]

Lets start cleaning up areas before obsoleting this starting in preview6.

• SignalR - [SignalR] Move to generic host #22602
• DataProtection Move DataProtection tests to HostBuilder #24254
• Middleware - [Middleware] Move to GenericHost #23626
  • Rewrite
  • Localization
  • Localization.Routing
  • StaticFiles
  • HttpsPolicy
  • HttpOverrides
  • WebSockets
  • Diagnostics
  • HostFiltering
  • ResponseCaching
  • Session
  • HealthChecks
  • CORS
  • Diagnostics.EntityFrameworkCore
  • MiddlewareAnalysis
  • ResponseCompression
  • ConcurrencyLimiter
  • NodeServices
  • HeaderPropagation
• Kestrel [Kestrel] Move to GenericHost #24279
• IIS [IIS] Move to GenericHost #24280
• Routing [Routing] Move to GenericHost #24281
• Security
  • Authentication Switch to new host apis #23783
  • CookiePolicy [Security] Move to GenericHost #24282
• Identity Switch to new host apis #23783
• Azure [Azure] Move to GenericHost #24283
• MVC
• MusicStore [MusicStore] Move to GenericHost #24284
• HttpSys [HttpSys] Move to GenericHost #24285
• Hosting [Hosting] Move to GenericHost #24297