Unable to create a constant value - only primitive types

Question

Two simple queries - the exception occurs in :

matchings.Any(u => product.ProductId == u.ProductId)

What is wrong? If I write true

Answer 1

This looks like a place to use join

 var query =
    from product in db.Products
    join matching in db.Matchings
    on product.ProductId equals matching.ProductId into matchGroup
    where matchGroup.Count() > 0 and matching.StoreId == StoreId
    select product;