Linq查询以查找所有孤儿产品 [英] Linq query to find all orphan products

问题描述

对于产品和产品类别系统，我有三种模型:

I have three models for a product and product category system:

[Products]
Id
Title
Info
Price

[ProductCategories]
Id
ParentId
SortOrder
Title

[ProductsInCategories]
Id
ProductId
ProductCategoryId
SortOrder

现在，我要列出在ProductsInCategories表中没有条目的所有产品的列表.即所有孤儿产品.如何在linq中做到这一点?

Now, I want to make a list of all products which doesn't have an entry in the ProductsInCategories table. I.e., all orphan products. How can I do that in linq?

推荐答案

您可以使用！Any 来仅获取在 ProductsInCategories 中没有条目的那些人:

You can use !Any to get only those without an entry in ProductsInCategories:

List<Product> productList = db.Products
    .Where(p => !db.ProductsInCategories.Any(pc => p.Id == pc.ProductId))
    .ToList();

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