asp.net DirectoryEntry error

Imports System
Imports System.Data
Imports System.Linq
Imports System.IO
Imports System.DirectoryServices
Imports System.DirectoryServices.AccountManagement
Imports System.DirectoryServices.ActiveDirectory
Imports System.Security
Imports System.Security.Permissions
Imports System.Text
Imports System.Collections
Imports System.ComponentModel
Imports System.Drawing
Imports System.Web
Imports System.Web.SessionState
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Web.UI.HtmlControls
 
Partial Class _Default
    Inherits System.Web.UI.Page
 
    Public Function EnumerateDomains() As ArrayList
        Dim alDomains As New ArrayList()
        Dim currentForrest As Forest = Forest.GetCurrentForest()
        Dim myDomains As DomainCollection = currentForrest.Domains
        For Each objDomain As Domain In myDomains
            alDomains.Add(objDomain.Name)
        Next
        Return alDomains
    End Function
 
    Protected Sub Selection_Changed(ByVal sender As Object, _
   ByVal e As System.EventArgs) Handles Me.Load
        DropDownList1.Items.Clear()
        DropDownList1.AppendDataBoundItems = True
        DropDownList1.SelectedIndex = 0
        DropDownList1.DataSource = EnumerateDomains()
        DropDownList1.DataBind()
        'Dim dUsers As String = DropDownList1.SelectedItem.ToString()
    End Sub
 
    Public Function EumerateDomainUsers() As ArrayList
        Dim domainUsers As New ArrayList()
        Dim usr As String
        'Dim fqdns As String = DropDownList1.SelectedItem.ToString()
        Dim fqdns As String = DropDownList1.SelectedItem.Text
        Dim adStrng As String = "LDAP://" & fqdns
        Dim adEntry As DirectoryEntry = (adStrng)
        Dim searcher As DirectorySearcher = New DirectorySearcher(adEntry)
        searcher.Sort.PropertyName = "cn"
        Dim results As SearchResultCollection
        Dim result As SearchResult
        searcher.PropertiesToLoad.Add("cn")
        results = searcher.FindAll
        For Each result In results
            usr = result.GetDirectoryEntry().Properties("cn").Value
            domainUsers.Add(usr)
        Next
        Return domainUsers
    End Function
 
    Protected Sub Selection_Changed1(ByVal sender As Object, _
  ByVal e As System.EventArgs) Handles Me.Load
        DropDownList2.Items.Clear()
        DropDownList2.AppendDataBoundItems = True
        DropDownList2.SelectedIndex = 0
        DropDownList2.DataSource = EumerateDomainUsers()
        DropDownList2.DataBind()
        'Dim dUsers As String = DropDownList1.SelectedItem.ToString()
    End Sub
End Class

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