Typed ClaimsPrincipal sketch

TypedClaimsPrincipal.cs

using System.Security.Claims;
using Microsoft.AspNetCore.Http;

namespace TypedClaimsPrincipal;

public interface IClaimsPrincipalProperties<out T>
    where T : IClaimsPrincipalProperties<T>
{
    static abstract T Create(ClaimsPrincipal claimsPrincipal);
}

public class ClaimsPrincipal<T>
    where T : class, IClaimsPrincipalProperties<T>, new()
{
    private readonly ClaimsPrincipal _principal;
    private T? _properties;

    public ClaimsPrincipal(ClaimsPrincipal principal)
    {
        _principal = principal;
    }

    public T Properties => _properties ??= T.Create(_principal);
}

public class MyClaimsProperties : IClaimsPrincipalProperties<MyClaimsProperties>
{
    private readonly ClaimsPrincipal _principal;
    private Guid? _userId;

    public MyClaimsProperties(ClaimsPrincipal claimsPrincipal)
    {
        _principal = claimsPrincipal;
    }

    public static MyClaimsProperties Create(ClaimsPrincipal claimsPrincipal)
    {
        return new MyClaimsProperties(claimsPrincipal);
    }

    public Guid UserId => _userId ??= Guid.Parse(_principal.FindFirstValue("UserId"));
}

public static class HttpContextExtension
{
    public static ClaimsPrincipal<T> GetTypedUser<T>(this HttpContext context)
        where T : class, IClaimsPrincipalProperties<T>, new()
    {
        var instance = context.Features.Get<ClaimsPrincipal<T>>();
        if (instance is null)
        {
            instance = new ClaimsPrincipal<T>(context.User);
            context.Features.Set(instance);
        }

        return instance;
    }
}