How to convert IQueryable <T> to ObjectQuery <T>?

Question

I am trying to apply advice in this post: Tip 22 - How to enable Enable really Enable

It offers a workaround for providing reliable boot operations in the Entity Framework (4.2). This method involves casting IQueryable in ObjectQuery.

However, when I try to do this, as shown in the message, the query returns zero.

My request (ctx is DbContext):

IEnumerable<Coupon> coupons = from x in ctx.Coupons where x.LanguageCode.Equals("EN", StringComparison.InvariantCultureIgnoreCase) && x.CategoryId == MainCategoryId && x.Date >= fromDate && x.Date <= toDate select x; 

This works as expected.

However, when I use

 IEnumerable<Coupon> coupons = (from x in ctx.Coupons where x.LanguageCode.Equals("EN", StringComparison.InvariantCultureIgnoreCase) && x.CategoryId == MainCategoryId && x.Date >= fromDate && x.Date <= toDate select x) as ObjectQuery<Coupon>; 

it assigns null to "coupons".

Any idea what I'm doing wrong?

Answer 1

From the comments to the answer:

Listing ObjectQuery<T> only works when the query is really ObjectQuery<T> , it will not work on any other IQueryable<T> . Since you are using a DbContext instead of an ObjectContext , the requests are of a different type. However, you do not need to specify the correct type; the extension methods DbExtensions.Include in the System.Data.Entity namespace accept any type of IQueryable<T> and call the corresponding base Include method. You can use this, avoid casting, and thereby avoid explicitly specifying the type of request in your code.

Answer 2

What you do is equivalent to this

 IEnumerable<Coupon> coupons = from x in ctx.Coupons where x.LanguageCode.Equals("EN", StringComparison.InvariantCultureIgnoreCase) && x.CategoryId == MainCategoryId && x.Date >= fromDate && x.Date <= toDate select x; ObjectQuery<Coupon> converted = coupons as ObjectQuery<Coupon>; 

with coupons not null and converted null.

This means that the order is missing.
This does not solve your problem, but at least identifies it.

Perhaps you are using a different version of Entity Framework?