Validate windows password from c# winform application

Imports System
Imports System.Runtime.InteropServices
Imports System.Security.Principal
Imports System.Security.Permissions
 
<Assembly: SecurityPermissionAttribute(SecurityAction.RequestMinimum, UnmanagedCode:=True), _
 Assembly: PermissionSetAttribute(SecurityAction.RequestMinimum, Name:="FullTrust")> 
Module Inpersonation
    Public mptTokenHandle As New IntPtr(0)
    Public mImpersonatedUser As WindowsImpersonationContext
 
    Private Declare Auto Function LogonUser 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 Boolean
 
    <DllImport("kernel32.dll")> _
    Private Function FormatMessage(ByVal dwFlags As Integer, ByRef lpSource As IntPtr, _
        ByVal dwMessageId As Integer, ByVal dwLanguageId As Integer, ByRef lpBuffer As [String], _
        ByVal nSize As Integer, ByRef Arguments As IntPtr) As Integer
    End Function
 
    Private Declare Auto Function CloseHandle Lib "kernel32.dll" (ByVal handle As IntPtr) As Boolean
 
    Private Declare Auto Function DuplicateToken Lib "advapi32.dll" (ByVal ExistingTokenHandle As IntPtr, _
            ByVal SECURITY_IMPERSONATION_LEVEL As Integer, _
            ByRef DuplicateTokenHandle As IntPtr) As Boolean
 
    <PermissionSetAttribute(SecurityAction.Demand, Name:="FullTrust")> _
    Public Function Impersonate(ByVal strUserId As String, ByVal strPassword As String, ByVal strDomainName As String) As Boolean
 
        Try
            Const LOGON32_PROVIDER_DEFAULT As Integer = 0
            Const LOGON32_LOGON_INTERACTIVE As Integer = 2
 
            'Call LogonUser to obtain a handle to an access token.
            mptTokenHandle = IntPtr.Zero
            Dim bolSuccess As Boolean = LogonUser(strUserId, strDomainName, strPassword, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, mptTokenHandle)
 
            If Not bolSuccess Then
                'MsgBox("UserId: " & strUserId & "  Domain: " & strDomainName & "  Password: " & strPassword)
                MsgBox("Impersonate() failed! Error is: Login failed for user: " & strUserId.Trim(), MsgBoxStyle.Critical, "Critical error")
                Return False
            End If
 
            'Use the token handle returned by LogonUser.
            Dim newId As New WindowsIdentity(mptTokenHandle)
            mImpersonatedUser = newId.Impersonate()
 
            'Check the identity.
            'MsgBox("After impersonation name: " & WindowsIdentity.GetCurrent().Name)
 
        Catch ex As Exception
            MsgBox("Impersonate() failed! Error is: " & ex.Message, MsgBoxStyle.Critical, "Critical error")
            Return Nothing
        End Try
 
        Return True
    End Function
 
    Public Sub UnImpersonate()
        Try
            'Stop impersonating the user.
            mImpersonatedUser.Undo()
 
            'Check the identity.
            'MsgBox("After Undo name: " + WindowsIdentity.GetCurrent().Name)
 
            'Free the tokens.
            If Not System.IntPtr.op_Equality(mptTokenHandle, IntPtr.Zero) Then CloseHandle(mptTokenHandle)
 
        Catch ex As Exception
            MsgBox("UnImpersonate() failed! Error is: " & ex.Message, MsgBoxStyle.Critical, "Critical error")
        End Try
    End Sub
End Module

                                              

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