如何在 Visual Studio 2022 中使用 .NET 6 Preview Generic Math？

Question

There are several articles explaining the new .NET 6 Preview features of Generic Math, often based on this Microsoft article:

https://devblogs.microsoft.com/dotnet/preview-features-in-net-6-generic-math/

In the preview versions, and the first release of Visual Studio 2022 this works fine. But in Visual Studio 2022 version 17.0.3 and 17.0.4 (the current release) I simply cannot get this to compile.

I actually went back to VS2022 version 17.0.0 to make sure I had correctly followed the article steps. The code compiles just fine. Upgrade to VS2022 version 17.0.3 and the same project fails to build with the error:

Error   CS0246  The type or namespace name 'INumber<>' could not be found (are you missing a using directive or an assembly reference?)

Anyone got any ideas? I assume I have to make a further change to the csproj file, but what change?

In the NuGet Package Manager I found the option to upgrade System.Runtime.Experimental to version 6.0.0, which changed the entry in my csproj file from:

  <ItemGroup>
    <PackageReference Include="System.Runtime.Experimental" Version="6.0.0-preview.7.21377.19" />
  </ItemGroup>

to:

  <ItemGroup>
    <PackageReference Include="System.Runtime.Experimental" Version="6.0.0" />
  </ItemGroup>

rebooting doesn't help. Cleaning the solution doesn't help. I am not seeing anything to help me in the release notes for Visual Studio 2022 either.

The complete csproj file, for reference, already containing the extra bits you need, is:

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

    <PropertyGroup>
        <OutputType>Exe</OutputType>
        <TargetFramework>net6.0</TargetFramework>
        <ImplicitUsings>enable</ImplicitUsings>
        <Nullable>enable</Nullable>
        <EnablePreviewFeatures>True</EnablePreviewFeatures>
        <LangVersion>preview</LangVersion>
    </PropertyGroup>

    <ItemGroup>
        <PackageReference Include="System.Runtime.Experimental" Version="6.0.0" />
    </ItemGroup>
</Project>

Answer 1

Step 1

As explained in the blog article you've linked at the top of the question: add

    <EnablePreviewFeatures>true</EnablePreviewFeatures>

into a <PropertyGroup> element in your project file.

Step 2

Now the above is confirmed: have you tried the preview version of VS2022 (currently V17.1 Preview 1.1)?

Just tried it: No.

Step 3

See Hans Passant's comment on to the question: need to wait on this (or do you own builds of what is being built to be .NET 7...)

Answer 2

I got the same error with VS2022 17.0.4. Now, VS2022 17.1.0 Preview 1.1 seems to work fine.