Join between in memory collection and EntityFramework

Question

Is there any mechanism for doing a JOIN between an in-memory collection and entity framework while preserving the order.

What I am trying is

var ite         


        

Answer 1

try this:

var list = (from n in efRepo
           where myInMemoryList.Select(m=>m.RECORD_NUMBER).Contains(n.RECORD_NUMBER)
           select n).ToList();

Contains will be translated to IN operator in SQL (only if your RECORD_NUMBER member is a primitive type like int, string, Guid, etc)

Answer 2

You can read how you can do this with the PredicateBuilder from the LINQKit or Stored Procedures in my blog post.

http://kalcik.net/2014/01/05/joining-data-in-memory-with-data-in-database-table/

Answer 3

No you cannot join in-memory collection with database result set without loading whole result set to the memory and performing the join with linq-to-objects. Try using contains instead of join:

var myNumbers = myInMemoryList.Select(i => i.RECORD_NUMBER);
var itemsToAdd = efRepo.Where(e => myNumbers.Contains(e.RECORD_NUMBER));

This will generate query with IN operator

Answer 4

What about loading the whole efRepo? I mean something like this (ToArray()):

var itemsToAdd = myInMemoryList.Join(
    efRepo.ToArray(),
    listitem => listitem.RECORD_NUMBER, efRepoItem => efRepoItem.RECORD_NUMBER, (left, right) => right);