Show Domain User Name on Web Page

I've searched and can't find anything about displaying domain user name on a webpage - just on authentication.  My web page has a field that when the form loads, I want it to show the name of the user logged onto that computer.  I does this by looking at the domain user name logged onto that computer, and getting the name from a SQL table that equals that domain name.  It works when I display in in Visual Studio 2010, but after I publish it (IIS), the name is blank.  Here is my vb code:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load 'Dim windowsIdentity As System.Security.Principal.WindowsIdentity = System.Security.Principal.WindowsIdentity.GetCurrent 'Dim windowsLoginName As System.String = windowsIdentity.Name Dim windowsLoginName As System.String = System.Security.Principal.WindowsIdentity.GetCurrent().Name Dim split As String() = Nothing ...