IWebAccount2 - C#/WinRT

foo.csproj

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

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net7.0-windows10.0.22000.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
    <!-- **** IMPORTANT 1 - Add the Windows.Security namespace to the list of generated projections -->
    <CsWinRtIncludes>Windows.Security</CsWinRtIncludes>
  </PropertyGroup>

  <ItemGroup>
    <!-- **** IMPORTANT 2 - This generates the projections -->
    <PackageReference Include="Microsoft.Windows.CsWinRT" Version="2.0.2" />
  </ItemGroup>

</Project>

Program.cs

using Windows.Security.Credentials;
using WinRT;

namespace CredentialCsWinRtTest {
    internal class Program {
        static void Main(string[] args) {
            Windows.Security.Credentials.WebAccount foo = null /* or somehow get it */;
            Windows.Security.Credentials.IWebAccount2 webAccount2 = foo.As<IWebAccount2>();
            // if webaccount2 is not null . . .
            webAccount2.SignOutAsync("clientId"); // do something with the async task actually
        }
    }
}

It is probably important to set the TFM to include -windows10.0.xxxxx, where that number is one of the Windows SDKs you have installed.