SharePoint Page Navigation Web Part

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Security.Principal;
using System.ComponentModel;

namespace Mullivan.Security
{
    public static class CredentialImpersonate
    {
        private const int LOGON32_LOGON_INTERACTIVE = 2;
        private const int LOGON32_PROVIDER_DEFAULT = 0;

        public static WindowsImpersonationContext Impersonate(string domain, string userName, string password)
        {
            IntPtr token = IntPtr.Zero;
            IntPtr tokenDuplicate = IntPtr.Zero;

            try
            {
                if (LogonUser(userName, domain, password, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, ref token))
                {
                    if (DuplicateToken(token, 2, ref tokenDuplicate) != 0)
                    {
                        return new WindowsIdentity(tokenDuplicate).Impersonate();
                    }
                    else
                        throw new Win32Exception(Marshal.GetLastWin32Error(), "DuplicateToken Failed");
                }
                else
                    throw new Win32Exception(Marshal.GetLastWin32Error(), "LogonUser Failed");
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                if (token != IntPtr.Zero)
                    CloseHandle(token);

                if (tokenDuplicate != IntPtr.Zero)
                    CloseHandle(tokenDuplicate);
            }
        }

        [DllImport("advapi32.dll", SetLastError = true)]
        private static extern bool LogonUser(
            String lpszUsername,
            String lpszDomain,
            String lpszPassword,
            int dwLogonType,
            int dwLogonProvider,
            ref IntPtr phToken);

        [DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern int DuplicateToken(IntPtr hToken,
            int impersonationLevel,
            ref IntPtr hNewToken);

        [DllImport("kernel32.dll", CharSet = CharSet.Auto)]
        private static extern bool CloseHandle(IntPtr handle);
    }
}