using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Permissions;
using System.Security.Principal;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace ConsoleApplication10
{
    class Program
    {
        static void Main(string[] args)
        {
            GenericIdentity id = new GenericIdentity("username");
            GenericPrincipal p = new GenericPrincipal
            (id, new string[] { "Zzz"});
            Thread.CurrentPrincipal = p;

            try
            {
                MyMethod();
            }
            catch (SequrityException ex)
            {
                Console.WriteLine(ex);
            }
        }

        [PrincipalPermission(SecurityAction.Demand, Role="Zzz")]
        static void MyMethod()
        {
            Console.WriteLine("Здоровэньки булы!");
        }
    }
}