团体加入linq，但仅限于儿童在场的情况

我有一个简单的查询，我希望有一个类别列表，以及每个类别中的产品数量

from category in categories
join product in products
    on category.Id equals product.Category_Id into productsPerCategories
select new Categories
{
    Category = category,
    products = productsPerCategories.Count()
};

但是如果没有产品，我不希望出现该类别。在我当前的构造中，将有没有产品的类别。我怎样才能做到这一点呢？

只需添加一个条件即可

where productsPerCategories.Any()

或

所以你的问题是：

from category in categories
join product in products on category.Id equals product.Category_Id into productsPerCategories
where productsPerCategories.Any()

            select new Categories
            {
                Category = category,
                products = productsPerCategories.Count()
            };

from category in categories
join product in products on category.Id equals product.Category_Id into productsPerCategories
where productsPerCategories.Any()

            select new Categories
            {
                Category = category,
                products = productsPerCategories.Count()
            };