Development often requires impersonation with Sharepoint (MOSS) 2007

  public class Impersonator
  {
    public string CurrentUser
    {
      get
      {
        return this.username;
      }
    }

    public string Domain
    {
      get
      {
        return this.domain;
      }
    }

    // private members for holding domain user account credentials
    private string username = String.Empty;
    private string password = String.Empty;
    private string domain = String.Empty;
    // this will hold the security context for reverting back to the client after impersonation operations are complete
    private WindowsImpersonationContext impersonationContext = null;

    // disable instantiation via default constructor
    private Impersonator()
    { }

    public Impersonator(string username, string domain, string password)
    {
      // set the properties used for domain user account
      this.username = username;
      this.domain = domain;
      this.password = password;
    }

    private WindowsIdentity Logon()
    {
      IntPtr handle = new IntPtr(0);
      handle = IntPtr.Zero;

      // This stuff required for impersonation
      //const int LOGON32_LOGON_NETWORK = 3;
      //const int LOGON32_LOGON_SERVICE = 3;
      const int LOGON32_PROVIDER_DEFAULT = 0;
      const int LOGON32_LOGON_INTERACTIVE = 2;

      // attempt to authenticate domain user account
      // bool logonSucceeded = LogonUser(this.username, this.domain, this.password, LOGON32_LOGON_NETWORK, LOGON32_PROVIDER_DEFAULT, ref handle);
      bool logonSucceeded = LogonUser(this.username, this.domain, this.password, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, ref handle);

      if (!logonSucceeded)
      {
        // if the logon failed, get the error code and throw an exception
        int errorCode = Marshal.GetLastWin32Error();
        throw new Exception("User logon failed. Error Number: " + errorCode);
      }

      // if logon succeeds, create a WindowsIdentity instance
      WindowsIdentity winIdentity = new WindowsIdentity(handle);

      // close the open handle to the authenticated account
      CloseHandle(handle);

      return winIdentity;
    }


    public void Impersonate()
    {
      // authenticates the domain user account and begins impersonating it
      this.impersonationContext = this.Logon().Impersonate();
    }


    public void Undo()
    {
      // rever back to original security context which was store in the WindowsImpersonationContext instance
      this.impersonationContext.Undo();
    }

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

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

  }