Given LINQ to Entities does not support “Custom methods” how do you stay DRY?

Question

I have run into this problem:

Custom Methods & Extension Methods cannot be translated into a store expression

Basically I have some complicated LINQ quer

Answer 1

EF can't compose a query out of a LINQ expression that includes a method. EF needs literal values to compose the SQL.

You will have to make do with "common" queries that return a superset of the Entities you need for a given case, then use extension methods and LINQ to narrow down the return set once it has been returned from the database.