A LINQ to SQL query can include calls to your own local methods:

158.

In Where clauses only

In the final projection only

Anywhere in the query

Not at all

In a LINQ to SQL query, you cannot include calls to your own local methods (or unsupported Framework methods) in any place other than the final projection. If you try to do otherwise, one of two things will happen:

LINQ to SQL will throw an exception when the query executes ("method XYZ has no translation to SQL")
the query will be executed locally from that point on.