Disjoint queries in LINQ to SQL

I find LINQ to SQL expressions very useful when running queries against Entity Framework objects; however, running disjoint queries in LINQ (queries that require filtering one list and running the results against another) is not as simple using inner joins or correlated sub-queries [i.e.  in SQL "where [someID] not in ([some query])']. To run a disjoint query in LINQ to SQL you would have to write three separate queries.

One with all data you need

Code Snippet

44. var myDataUniverse = from ent in [SomeEntity]
45.                      select ent;

another with items to exclude

Code Snippet

47. var myExcludedList = from ent in [SomeEntity]
48.                       // where some logic to filter excluded entities
49.                      select ent;

and finally disjoin them.

Code Snippet

51. var myFinalList = myDataUniverse.Except(myExcludedList);

Caveat: Entities in the disjoint query must be of the same type or must have an IEqualityComparer interface defined for the Except function to execute without run-time errors.

You might want to consider using the Concat or Union  LINQ functions, in case your business logic calls for combining objects into a single list.