I am writing a web page that I want to use pass through user authentication from the network. I am using DirectoryServices to get the current logon username and authenticating it against a database of users who are authorized to access the site. The problem I am having is that I am getting an error when I try to get the path with "Dim strRoodDAE As String = DSearcher.SearchRoot.Path".

I am able to run the function without error if I use the Visual Studio built in "View in Browser" option that uses port 1345 to show the page, but if I go to the normal port 80 page and click the button to process the function i get the following error: 

Error:

    Exception Details: System.Runtime.InteropServices.COMException: The specified domain either does not exist or could not be contacted.

VB Function:

    Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
        Dim DSearcher As New DirectoryServices.DirectorySearcher
        Dim strRootDAE As String = DSearcher.SearchRoot.Path
        Dim Dentry As New DirectoryServices.DirectoryEntry(strRootDAE)
        DSearcher.Filter = "(& (mailnickname=" & txtLanID.Text & ")(objectClass=user))"
        DSearcher.SearchScope = DirectoryServices.SearchScope.Subtree
        DSearcher.PropertiesToLoad.Add("mail")
        DSearcher.PropertiesToLoad.Add("givenname")
        DSearcher.PropertiesToLoad.Add("sn")
        DSearcher.PropertyNamesOnly = True
        Dim colSearchResults As DirectoryServices.SearchResultCollection
        colSearchResults = DSearcher.FindAll
        Dim strEmail As String = ""
        For Each sResult As DirectoryServices.SearchResult In colSearchResults
            Me.txtEmail.Text = sResult.GetDirectoryEntry.Properties("mail").Value.ToString
            Me.txtFirstName.Text = sResult.GetDirectoryEntry.Properties("givenname").Value.ToString
            Me.txtLastName.Text = sResult.GetDirectoryEntry.Properties("sn").Value.ToString
        Next
    End Sub

Stack Trace:

[COMException (0x8007054b): The specified domain either does not exist or could not be contacted.
]
   System.DirectoryServices.DirectoryEntry.Bind(Boolean throwIfFail) +377678
   System.DirectoryServices.DirectoryEntry.Bind() +36
   System.DirectoryServices.DirectoryEntry.get_AdsObject() +31
   System.DirectoryServices.PropertyValueCollection.PopulateList() +26
   System.DirectoryServices.PropertyValueCollection..ctor(DirectoryEntry entry, String propertyName) +49
   System.DirectoryServices.PropertyCollection.get_Item(String propertyName) +150
   System.DirectoryServices.DirectorySearcher.get_SearchRoot() +92
   DOU.frmAddUser.Button1_Click(Object sender, EventArgs e) in C:\Inetpub\wwwroot\frmAddUser.aspx.vb:12
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +111
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +110
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1565

If you are using a serverless bind (no server or DNS name in the path, just
a DN), then it may fail. Serverless bind requires a domain security context
to determine the domain to contact. If the current security context in the
web app is a local machine account, you will get this failure. You can
simulate the problem by logging in with a local machine account and running
the console app.

To find the current security context, do
System.Security.Principal.WindowsIdentity.GetCurrent().Name. 

You have identified the problem correctly.  I do not use the view-in-browser, but you need to specify the AD donain you are binding while creating the directory entry.  The equvalent C# is:

         System.DirectoryServices.DirectoryEntry entry =  new System.DirectoryServices.DirectoryEntry("LDAP://YourDomainControl.com/OU=...DC=...");