ASP.NET

   Imports Microsoft.VisualBasic
Imports System.Web.Security
Imports System.Security.Principal
Imports System.Runtime.InteropServices
Imports System.Threading
Imports System.Configuration
Imports SR = System.Reflection
Imports System.Text
Imports System.Web.UI.WebControls

Public Class Impersonation
    Private Const LOGON32_PROVIDER_DEFAULT As Integer = 0
    Private Const LOGON32_LOGON_INTERACTIVE As Integer = 2
    Private Const LOGON32_LOGON_NETWORK As Integer = 3
    Private Const LOGON32_LOGON_BATCH As Integer = 4
    Private Const LOGON32_LOGON_SERVICE As Integer = 5
    Private Const LOGON32_LOGON_UNLOCK As Integer = 7
    Private Const LOGON32_LOGON_NETWORK_CLEARTEXT As Integer = 8
    Private Const LOGON32_LOGON_NEW_CREDENTIALS As Integer = 9

    Private Shared ImpersonationContext As WindowsImpersonationContext

    Declare Function LogonUserA Lib "advapi32.dll" ( _
                            ByVal lpszUsername As String, _
                            ByVal lpszDomain As String, _
                            ByVal lpszPassword As String, _
                            ByVal dwLogonType As Integer, _
                            ByVal dwLogonProvider As Integer, _
                            ByRef phToken As IntPtr) As Integer

    Declare Auto Function DuplicateToken Lib "advapi32.dll" ( _
                            ByVal ExistingTokenHandle As IntPtr, _
                            ByVal ImpersonationLevel As Integer, _
                            ByRef DuplicateTokenHandle As IntPtr) As Integer
    Declare Auto Function RevertToSelf Lib "advapi32.dll" () As Long
    Declare Auto Function CloseHandle Lib "kernel32.dll" (ByVal handle As IntPtr) As Long

    Public Shared Function ImpersonateValidUser(ByVal strUserName As String, _
                   ByVal strDomain As String, ByVal strPassword As String) As Boolean
        Dim token As IntPtr = IntPtr.Zero
        Dim tokenDuplicate As IntPtr = IntPtr.Zero
        Dim tempWindowsIdentity As WindowsIdentity

        ImpersonateValidUser = False

        If RevertToSelf() <> 0 Then
            If LogonUserA(strUserName, strDomain, _
               strPassword, _
               LOGON32_LOGON_INTERACTIVE, _
               LOGON32_PROVIDER_DEFAULT, token) <> 0 Then
                If DuplicateToken(token, 2, tokenDuplicate) <> 0 Then
                    tempWindowsIdentity = New WindowsIdentity(tokenDuplicate)
                    ImpersonationContext = tempWindowsIdentity.Impersonate()

                    If Not (ImpersonationContext Is Nothing) Then
                        ImpersonateValidUser = True
                        
                    End If
                End If
            End If
        End If

        If Not tokenDuplicate.Equals(IntPtr.Zero) Then
            CloseHandle(tokenDuplicate)
        End If

        If Not token.Equals(IntPtr.Zero) Then
            CloseHandle(token)
        End If

    End Function

    Public Shared Sub UndoImpersonation()

        ImpersonationContext.Undo()

    End Sub
End Class