Deprecating WebHostBuilder, IWebHost, and WebHost

[BrennanConroy]

Discussion for announcement aspnet/Announcements#526

[julealgon]

Why not deprecate HostBuilder as well? Don't you want everyone to move to the new HostApplicationBuilder-based API?

I don't see a point in maintaining anything other than the new HostApplicationBuilder approach. It is superior to the previous method in every way. Having both available is quite confusing.

[martincostello]

FWIW, I would have had to refactor a lot more tests in some projects if that had been deprecated too 😅

[davidfowl]

The new interface IHostApplicationBuilder exists in .NET 9 only so it's tough to deprecate HostBuilder and IHostBuilder because many people have never used IHostApplicationBuilder. Going forward though we'll recommand HostApplicationBuilder and IHostApplicationBuilder

[julealgon]

Fair enough. Thanks @davidfowl .

[ScarletKuro]

The new interface IHostApplicationBuilder exists in .NET 9 only so it's tough to deprecate HostBuilder and IHostBuilder because many people have never used IHostApplicationBuilder. Going forward though we'll recommand HostApplicationBuilder and IHostApplicationBuilder

I'm confused. How is this tied to .NET 9? Doesn't it live in Microsoft.Extensions.Hosting.Abstractions starting from v8, making it available even to .NET Framework 4.6.2 and .NET Standard 2.0?

I'd also like to see IHostBuilder deprecated (but not removed just yet). I understand that tons of libraries still use IHostBuilder, but deprecating it would actually push people to adapt their designs to IHostApplicationBuilder. Eventually, it could be removed after a few major releases.

[Lanayx]

The After example seems to be misleading:

using var host = new HostBuilder()
    .ConfigureWebHost(webHostBuilder =>
    {
        webHostBuilder
            .UseTestServer() // If using TestServer
            .UseContentRoot(Directory.GetCurrentDirectory())
            .UseStartup()
            .UseKestrel(); // <--- This line should be deleted
    })
    .Build();
await host.StartAsync();

var testServer = host.GetTestServer();

While .UseKestrel worked fine in Before version, in After version it leads to the following exception

System.InvalidCastException
Unable to cast object of type 'Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServerImpl' to type 'Microsoft.AspNetCore.TestHost.TestServer'.

Once .UseKestrel is removed, everything works fine in new version. Remarkably, the advise to use ChatGPT worked - it didn't include that line while doing conversion.

[sadjadbp]

@BrennanConroy let's add a comment for .UseKestrel to be used for non test servers, as Lanayx mentioned above. I see same error

[simontom]

Hey guys, is there any way how to get this working after the change?
I mean, the injection stopped working. I'm aware there was some info a few years ago about this breaking(?) change.

[simontom]

Sorry I forgot to mention: currently using WebHost

[jpdurot]

Do you have any idea when/if those deprecated classes will be completely removed?