WebApi's linux builds fail when referencing HttpSys.

[SitamMatt]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

On Linux, when running dotnet build on project that targets .net10.0 and references .UseHttpSys() then build fails with error:

Program.cs(3,17): error CS1061: 'ConfigureWebHostBuilder' does not contain a definition for 'UseHttpSys' and no accessible extension method 'UseHttpSys' accepting a first argument of type 'ConfigureWebHostBuilder' could be found (are you missing a using directive or an assembly reference?)

However, when project targets .net9.0 or lower, then build succeeds on both Linux and Windows.

Expected Behavior

The described behaviour was not mentioned as breaking change, and building httpsys application should succeed on all platforms.

Steps To Reproduce

Program.cs:

var builder = WebApplication.CreateBuilder(args);

builder.WebHost.UseHttpSys();

var app = builder.Build();

app.Run();

Example.csproj:

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFrameworks>net10.0;net9.0;net8.0</TargetFrameworks>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
  </PropertyGroup>

</Project>

Run (both windows and linux platform)
dotnet build
dotnet build --framework net10.0
dotnet build --framework net9.0
dotnet build --framework net8.0

Exceptions (if any)

No response

.NET Version

10.0.100

Anything else?

No response

[MihuBot]

I'm a bot. Here is a possible related and/or duplicate issue (I may be wrong):

• Some Microsoft.AspNetCore.Server.HttpSys.dll APIs are not available on source-build #63782

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