c# - Entity Framework 5 and SQL Queries -

i facing serious performance issues... query supposed filter products sql directly in database. when execute code, doesn't, , returns products , filters them in c#.

mycontext context = new mycontext();  func<product, bool> query = (p => p.upc.startswith("817"));  var products = context.products.where(query).take(10); 

i've noticed products variable of type takeiterator. when change code slightly, filtering ok, forces me put query logic directly in same method, want avoid.

mycontext context = new mycontext();  var products = context.products.where(p => p.upc.startswith("817")).take(10); 

this second version of undisclosed type visual studio debugger, shows query trying end with, good!

{select top (10)  [extent1].[id] [id],  [extent1].[brand] [brand],  [extent1].[description] [description],  [extent1].[upc] [upc] [dbo].[products] [extent1] [extent1].[upc] n'817%'} 

i need figure out how func passed argument , execute query in same fashion first c# code excerpt, optimisations of second.

try instead:

mycontext context = new mycontext();  expression<func<product, bool>> query = (p => p.upc.startswith("817"));  var products = context.products.where(query).take(10); 

and see question reference on why:

why use expression<func<t>> rather func<t>?

the accepted answer there complete don't dare try explain better!