Identify the Active Directory Username from Silverlight app from Sharepoint

I needed to know the Active Directory username of the current user from my Silverlight app.  The Silverlight control is running from a Sharepoint site. 

It seems that this isn't as easy as you would think.  I found several ways, but the one I ended up using wasn't one of them.

1. Page.User.Identity.Name.Split('\\')[1];  - this would work from code behind or even in alligator tags in front end - but my Sharepoint page wouldn't allow them.
2. var wshshell=new ActiveXObject("wscript.shell");
   var username=wshshell.ExpandEnvironmentStrings("%usern ame%");

For i As Integer = 0 To Request.ServerVariables.Count - 1
Response.Write(Request.ServerVariables.Keys(i) & " : <br /> [ " & Request.ServerVariables(i) & " ] <br /> ")
Next

This one is totally hard to do under any type of security scenario.

1. HttpContext.Current.Profile.UserName  - again, this would work from code behind or even in alligator tags in front end - but my Sharepoint page wouldn't allow them.
2. <script type="text/vbscript" language="VBscript">
   Dim X
   set X = createobject("WSCRIPT.Network")
   dim U
   U=x.UserName
   'MsgBox "username: " & U
   </script>
   <script type="text/javascript" language="Javascript">
       var a = U;
       $("#name").text(a.toString());
   </script>

Hard to even print these two that use active x!  But for the sake of completeness, here they are.

AND - The way I used:

When my Silverlight app is loaded, the first thing I do is send a web service request to add a list item to a log list.  The list has only one field, that is Title.  So I add an "application opened" record to the log.   What I get in return is an xml confirmation that the record was added - the confirmation contains the name of the logged in user - which is their active directory name.  I just parse the correct element out "ows_Author" using XLinq and have what I needed.

Is this weird?  Cause I wouldn't be surprised!  Anyway, it works for me.