LDAP query not working in custom web part

I have a custom web part which will pull Active directories custom attribute(logged in user). For testing purpose currently I am trying to get "mail" of currently logged in user. But it is not working. Here is my code

DirectoryEntry entry = new DirectoryEntry("LDAP://rp.fs.asdf.org");
            DirectorySearcher mySearcher = new DirectorySearcher(entry, "(sAMAccountName=myuserid1)", new string[] { "mail" });
            mySearcher.PropertiesToLoad.Add("mail");
            SearchResult result = mySearcher.FindOne();
            if (result != null)
            {
                mailID = result.GetDirectoryEntry().Properties["mail"].Value.ToString();
            }
            entry.Close();
            entry.Dispose();
            mySearcher.Dispose();

The same code works perfectly in "Windows form". I have been fighting with this code. Please suggest some ideas. Appreciate your help.