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SYSLIB0002: PrincipalPermissionAttribute is obsolete

  • Article

The PrincipalPermissionAttribute constructor is obsolete and produces compile-time error SYSLIB0002, starting in .NET 5. You cannot instantiate this attribute or apply it to a method.

Unlike other obsoletion warnings, you can't suppress the error.

Workarounds

  • If you're applying the attribute to an ASP.NET MVC action method:

    Consider using ASP.NET's built-in authorization infrastructure. The following code demonstrates how to annotate a controller with an AuthorizeAttribute attribute. The ASP.NET runtime will authorize the user before performing the action.

    using Microsoft.AspNetCore.Authorization;

namespace MySampleApp
{
    [Authorize(Roles = "Administrator")]
    public class AdministrationController : Controller
    {
        public ActionResult MyAction()
        {
            // This code won't run unless the current user
            // is in the 'Administrator' role.
        }
    }
}

    For more information, see Role-based authorization in ASP.NET Core and Introduction to authorization in ASP.NET Core.

  • If you're applying the attribute to library code outside the context of a web app:

    Perform the checks manually at the beginning of your method by calling the IPrincipal.IsInRole(String) method.

    using System.Threading;

void DoSomething()
{
    if (Thread.CurrentPrincipal == null
        || !Thread.CurrentPrincipal.IsInRole("Administrators"))
    {
        throw new Exception("User is anonymous or isn't an admin.");
    }

    // Code that should run only when user is an administrator.
}

See also

PrincipalPermissionAttribute is obsolete as error