- if (Object.ReferenceEquals (sk1, sk2)
- || Object.ReferenceEquals (sk1.OriginalString,
- sk2.OriginalString))
+ if (sortkey1 == null)
+ throw new ArgumentNullException ("sortkey1");
+ if (sortkey2 == null)
+ throw new ArgumentNullException ("sortkey2");
+
+ if (Object.ReferenceEquals (sortkey1, sortkey2)
+ || Object.ReferenceEquals (sortkey1.OriginalString,
+ sortkey2.OriginalString))