I have a back end DB for an ERP system which has thousands of tables but all the relations between those tables are serviced by ERP itself.
When I need to write a query to that DB I have to make all the joins explicitly, which makes query ugly and must be repeated in each query. I cannot touch the DB itself - it is governed by ERP, but if I could specify relations between tables on LinqPad side, then I could use full power of Linq queries every time. The relations should be addable ad hoc, one at a time as needed, but LinqPad should remember them for future.