Attempt to join datatables on composite key gives error of 'could not find and implementation of query pattern'

I'm trying to learn how to query datatables and am attempting to join 2 tables on composite key as shown in linkhttp://msdn.microsoft.com/en-us/library/bb397941.aspxI didn't get far as I got the error 'could not find and implementation of query pattern for source type datatable'.  I tried with 'var items = ...' and received the same error.

I realize there are other ways but would like to get this under my belt.  I want to find entries in both tables and offer user option to delete and rebuild target or skip. 

What am I missing that is causing the error?

IEnumerable<string> items = from t1 in dtVX130
                        join t2 in distincttblPKIEN
                        on new { t1.dwTableName, t1.TargetSchema }
                             equals new { t2.DWPhysicalTableName, t2.DWPhysicalSchemaName }
                             select new { Tablename = t1.dwTableName, Schema = t1.TargetSchema };