Linq syntax to select nested objects

Question

I'm trying to filter an IEnumerable using some of its nested properties.

I've racked my brain every which way but cannot find a solution to this query. In fact I don't event know whether this is possible.

Its structure is like this

T is a Deal a Deal has a collection of Subcategories (the collection may be empty) a Subcategory has a SubcategoryId

I want to be able to select Deals whether they have a SubcategoryId = parameter that is passed to method.

Answer 1

public IEnumerable<Deal> FindDeals(IEnumerable<Deal> source, int subCategoryId)
{    
    return source.Where(d => d.Subcategories.Any(s => s.Id == subCategoryId));
}