ถามเรื่อง การใช้งาน ASP.NET กับ Authentication ผ่าน AD ครับ

Imports System.Text
Imports System.Collections
Imports System.DirectoryServices

Namespace FormsAuth
	Public Class LdapAuthentication
		Private _path As String
		Private _filterAttribute As String

		Public Sub New(path As String)
			_path = path
		End Sub

		Public Function IsAuthenticated(domain As String, username As String, pwd As String) As Boolean
			Dim domainAndUsername As String = domain & "\" & username
			Dim entry As New DirectoryEntry(_path, domainAndUsername, pwd)

			Try
				'Bind to the native AdsObject to force authentication.
				Dim obj As Object = entry.NativeObject

				Dim search As New DirectorySearcher(entry)

				search.Filter = "(SAMAccountName=" & username & ")"
				search.PropertiesToLoad.Add("cn")
				Dim result As SearchResult = search.FindOne()

				If result Is Nothing Then
					Return False
				End If

				'Update the new path to the user in the directory.
				_path = result.Path
				_filterAttribute = DirectCast(result.Properties("cn")(0), String)
			Catch ex As Exception
				Throw New Exception("Error authenticating user. " & ex.Message)
			End Try

			Return True
		End Function

		Public Function GetGroups() As String
			Dim search As New DirectorySearcher(_path)
			search.Filter = "(cn=" & _filterAttribute & ")"
			search.PropertiesToLoad.Add("memberOf")
			Dim groupNames As New StringBuilder()

			Try
				Dim result As SearchResult = search.FindOne()
				Dim propertyCount As Integer = result.Properties("memberOf").Count
				Dim dn As String
				Dim equalsIndex As Integer, commaIndex As Integer

				For propertyCounter As Integer = 0 To propertyCount - 1
					dn = DirectCast(result.Properties("memberOf")(propertyCounter), String)
					equalsIndex = dn.IndexOf("=", 1)
					commaIndex = dn.IndexOf(",", 1)
					If -1 = equalsIndex Then
						Return Nothing
					End If
					groupNames.Append(dn.Substring((equalsIndex + 1), (commaIndex - equalsIndex) - 1))
					groupNames.Append("|")
				Next
			Catch ex As Exception
				Throw New Exception("Error obtaining group names. " & ex.Message)
			End Try
			Return groupNames.ToString()
		End Function
	End Class
End Namespace