using System;
using System.Configuration;
using System.Diagnostics;
using System.Text.RegularExpressions;
using System.Security;
using System.Net;
using System.Security.Principal;
using System.Reflection;
using System.IO;


 public static void SetAlternateUser(string userName, string password, string domain)
    {
        // thread safe singleton code
        lock (threadSafeLock)
        {
            if (_ie == null)
            {
                StartIE();
            }

            _ie.Close();
            _ie = null;


            // fill the NetworkCredeitials object that we use for impersonation
            if (string.IsNullOrEmpty(domain))
            {
                alternateUserCredentials = new NetworkCredential(userName, password);
            }
            else
            {
                alternateUserCredentials = new NetworkCredential(userName, password, domain);
            }

            // Prepare to launch
            ProcessStartInfo psi = new ProcessStartInfo();
            psi.UserName = userName;
            psi.Password = SecurePassword(password);
            if (!string.IsNullOrEmpty(domain))
            {
                psi.Domain = domain;
            }
            psi.UseShellExecute = false;
            psi.LoadUserProfile = true;
            psi.FileName = "c:\Program Files\Internet Explorer\iexplore.exe";
            psi.Arguments = "about:blank";


            // launch
            Process proc = new Process();
            proc.StartInfo = psi;
            proc.Start();

            // Time to become an imposter
            hToken = IntPtr.Zero;
            hTokenDuplicate = IntPtr.Zero;

            if (Win32.LogonUser(alternateUserCredentials.UserName, alternateUserCredentials.Domain, alternateUserCredentials.Password, 2 /*LOGON32_LOGON_INTERACTIVE*/, 0 /*LOGON32_PROVIDER_DEFAULT*/, out hToken))
            {
                if (Win32.DuplicateToken(hToken, 2, out hTokenDuplicate))
                {
                    windowsIdentity = new WindowsIdentity(hTokenDuplicate);
                    impersonationContext = windowsIdentity.Impersonate();
                    System.Threading.Thread.Sleep(1000);

                    _ie = IE.AttachToIE(Find.ByUrl("about:blank"));

                }
            }
        }
    }