Question

I have a problem understanding and working with the Include command, primarily when working on a nopCommerce 1.9 site, but I have the same problem everywhere. I have searched the net, and on stackoverflow, but can’t seem to find anyone else having the same problem, so I guess it’s just me that is getting this wrong.

I think that the problem is very simple, but plainly: When I include the child entities when querying the parent entity, EF loads all of the entities, but not the collection which means that when I try and access the collection, EF goes back to the database to load the collection.

To clarify, consider the following:

var products = (from p in _context.Products.Include("NpProductVariants") select p).ToList();

var productvariant = products.ProductVariants[2]; //Loads the NpProductVariants collection

I think that the additional fetch is superflous, indeed, if I create an object to hold the navigation collection and code using the holder, I can avoid further fetches, but this is annoying i.e.

var products = (from p in _context.Products.Include("NpProductVariants") select new productholder() { product = p, variants = p.NpProductVariants }).ToList();

This proves that the collection is available during query execution because I can store it, but it doesn’t automatically appear as attached to the ObjectContext until I try and access properties which requires an extra query.

I think that the problem is clear, but what am I doing wrong?

Any help would be much appreciated.

Thanks.

Mark

Answer 1

You are including "NpProductVariants", but you are accessing ProductVariants.

There are two things you can do, depending on your actual EF model:

1. Change the Include to "ProductVariants":

   var products = _context.Products.Include("ProductVariants");
   

2. Change the property you access to NpProductVariants:

   var productvariant = products.NpProductVariants[2];