LINQ无法从实体框架中检索相关数据

Question

I have the following:

db.Products.Where(p=>p.Sectors.Where(s=>s.website_id == websiteObj.website_id)).Count();

websiteObj is not null and has valid data. There is a many to many relationship between products and sectors. Also, there is a 1 to many relationship between sectors and websites. I don't have direct access to products from website, I have to go through the website related sectors.

Anyway, this example works: db.Sectors.Where(p=>p.website_id == websiteObj.website_id)).Count();

But the issue is that the first LINQ query gives me the following errors: Delegate 'System.Func<BusinessObjects.Product,int,bool>' does not take 1 arguments. Cannot convert lambda expression to type 'string' because it is not a delegate type.

And a couple other errors.

Anyway, what am I doing wrong? This is my first attempt with LINQ. Thanks in advance.

Answer 1

I think you need Any in the inner query:

db.Products.Where(p => p.Sectors.Any(s => s.website_id == websiteObj.website_id))
           .Count();

This would return all Products with at least one sector with the specified website_id.

If you want all Products where all sectors belong to the specified website_id, simply use All instead of Any :

db.Products.Where(p => p.Sectors.All(s => s.website_id == websiteObj.website_id))
           .Count();