VB.NET:

Imports System.Security.Principal
Public Class JoeyIdentity
    Implements IIdentityPublic ReadOnly Property AuthenticationType() As String Implements System.Security.Principal.IIdentity.AuthenticationType
        Get
            Return "Authenticated by Joey"
        End Get
    End PropertyPublic ReadOnly Property IsAuthenticated() As Boolean Implements System.Security.Principal.IIdentity.IsAuthenticated
        Get
            Return True
        End Get
    End PropertyPublic ReadOnly Property Name() As String Implements System.Security.Principal.IIdentity.Name
        Get
            Return "Joey"
        End Get
    End Property
End Class

Imports System.Security.Principal
Public Class JoeyPrincipal
    Implements IPrincipal
    Private _Identity As IIdentity
    Private _Roles() As StringPublic Sub New(ByVal Identify As IIdentity, ByVal Roles As String())
        _Identity = Identify
        _Roles = Array.CreateInstance(GetType(String), Roles.Length)
        Roles.CopyTo(_Roles, 0)
        Array.Sort(_Roles)
    End SubPublic ReadOnly Property Identity() As System.Security.Principal.IIdentity Implements System.Security.Principal.IPrincipal.Identity
        Get
            Return _Identity
        End Get
    End PropertyPublic Function IsInRole(ByVal role As String) As Boolean Implements System.Security.Principal.IPrincipal.IsInRole
        Return Array.BinarySearch(_Roles, role) >= 0
    End Function
End Class

Imports System.Threading
Imports System.Security.PermissionsModule Module1Sub Main()
        Dim jIdentity As New JoeyIdentity
        Dim roles As String() = {"Developer"}
        Dim jPrincipal As New JoeyPrincipal(jIdentity, roles)
        Thread.CurrentPrincipal = jPrincipal
        Try
            TestDeveloper()
            TestSucker()
        Catch ex As Exception
            Console.WriteLine(ex.GetType.ToString + " caused by " + Thread.CurrentPrincipal.Identity.Name)
        End Try
        Try
            Dim pp As New PrincipalPermission("Joey", "Developer")
            pp.Demand()
            Console.WriteLine(Thread.CurrentPrincipal.Identity.Name + " is indeed a developer.")
            pp = New PrincipalPermission("Joey", "Sucker")
            pp.Demand()
        Catch ex As Exception
            Console.WriteLine(Thread.CurrentPrincipal.Identity.Name + " is indeed not a sucker.")
        End Try
        Console.Read()
    End Sub<PrincipalPermissionAttribute(SecurityAction.Demand, role:="Developer")> _
    Private Sub TestDeveloper()
        Console.WriteLine(Thread.CurrentPrincipal.Identity.Name + " is a developer.")
    End Sub<PrincipalPermissionAttribute(SecurityAction.Demand, role:="Sucker")> _
   Private Sub TestSucker()
        Console.WriteLine(Thread.CurrentPrincipal.Identity.Name + " is a sucker.")
    End SubEnd Module

C#:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Security.Principal;namespace UserAndDataSecurityCS
{
    class JoeyIdentity : IIdentity
    {
        #region IIdentity Memberspublic string AuthenticationType
        {
            get
            {
                return "Authenticated by Joey";
            }
        }public bool IsAuthenticated
        {
            get
            {
                return true;
            }
        }public string Name
        {
            get
            {
                return "Joey";
            }
        }#endregion
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Security.Principal;namespace UserAndDataSecurityCS
{
    class JoeyPrincipal : IPrincipal
    {
        private IIdentity _Identity;
        private string[] _Roles;public JoeyPrincipal(IIdentity Identity, string[] Roles)
        {
            _Identity = Identity;
            _Roles = new string[Roles.Length];
            Roles.CopyTo(_Roles, 0);
            Array.Sort(_Roles);
        }#region IPrincipal Memberspublic IIdentity Identity
        {
            get
            {
                return _Identity;
            }
        }public bool IsInRole(string role)
        {
            return Array.BinarySearch<string>(_Roles, role) >= 0;
        }#endregion
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Security.Permissions;
using System.Threading;namespace UserAndDataSecurityCS
{
    class Program
    {
        static void Main(string[] args)
        {
            JoeyIdentity jIdentify = new JoeyIdentity();
            string[] roles = { "Developer" };
            JoeyPrincipal jPrincipal = new JoeyPrincipal(jIdentify, roles);
            Thread.CurrentPrincipal = jPrincipal;
            try
            {
                TestDeveloper();
                TestSucker();
            }
            catch(Exception ex)
            {
                Console.WriteLine(ex.GetType().ToString() + " caused by " + Thread.CurrentPrincipal.Identity.Name);
            }
            try
            {
                PrincipalPermission pp = new PrincipalPermission("Joey", "Developer");
                pp.Demand();
                Console.WriteLine(Thread.CurrentPrincipal.Identity.Name + " is indeed a developer.");
                pp = new PrincipalPermission("Joey", "Sucker");
                pp.Demand();
            }
            catch
            {
                Console.WriteLine(Thread.CurrentPrincipal.Identity.Name + " is indeed not a sucker.");
            }
            Console.Read();
        }

        [PrincipalPermissionAttribute(SecurityAction.Demand, Role