Visual Basic

' Values used by the LogonUser function's logonType parameter
  Public Enum LogonType
      LOGON32_LOGON_INTERACTIVE = 2
      LOGON32_LOGON_NETWORK = 3
      LOGON32_LOGON_BATCH = 4
      LOGON32_LOGON_SERVICE = 5
      LOGON32_LOGON_UNLOCK = 7
      LOGON32_LOGON_NETWORK_CLEARTEXT = 8
      LOGON32_LOGON_NEW_CREDENTIALS = 9
  End Enum

  ' Values used by the LogonUser function's logonProvider parameter
  Public Enum LogonProvider
      LOGON32_PROVIDER_DEFAULT = 0
      LOGON32_PROVIDER_WINNT35 = 1
      LOGON32_PROVIDER_WINNT40 = 2
      LOGON32_PROVIDER_WINNT50 = 3
  End Enum

  Declare Function LogonUser Lib "advapi32.dll" Alias "LogonUserA" ( _
                                                                      ByVal username As String, _
                                                                      ByVal domain As String, _
                                                                      ByVal password As String, _
                                                                      ByVal logonType As LogonType, _
                                                                      ByVal logonProvider As LogonProvider, _
                                                                      ByRef token As IntPtr _
                                                                    ) As Integer

  Public Sub LetterTemplate()
   Dim username As String = "username"
   Dim domain As String = "domain"
   Dim password As String = "password"

   ' A handle to the user who will be impersonated
   Dim token As IntPtr
   ' Log the user into Windows.
    Dim bLogonSuccessful As Boolean = Convert.ToBoolean( _
          LogonUser( _
          username, domain, password, _
          LogonType.LOGON32_LOGON_NETWORK, _
          LogonProvider.LOGON32_PROVIDER_DEFAULT, token))

   If Not bLogonSuccessful Then
     "Return something"
   End If

  ' Create a WindowsIdentity object that represents the logged-in user.
  Dim ident As New System.Security.Principal.WindowsIdentity(token)
  ' Impersonate the user.
  Dim ctx As System.Security.Principal.WindowsImpersonationContext = ident.Impersonate()

  '...... some other code

  'Release the impersonation
  ctx.Undo()
End Sub

Private Sub Register_FormClosing(ByVal sender As System.Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles MyBase.FormClosing<br />
    Dim exitChoice As Windows.Forms.DialogResult<br />
    exitChoice = MessageBox.Show("Are you sure you want to exit?", "Exiting?", MessageBoxButtons.YesNo, MessageBoxIcon.Information, MessageBoxDefaultButton.Button2)<br />
    If exitChoice = Windows.Forms.DialogResult.Yes Then<br />
        Application.Exit()<br />
    Else<br />
        e.Cancel = True<br />
    End If<br />
End Sub