在单个查询中从多个表中选择记录计数

Question

我有一些模型（餐馆，商店，产品），我想在单个linq查询中为多个模型选择记录数。

我知道它应该在sql中，但我不知道如何在linq中翻译它：

select
    (select count(*) from restaurants) as restaurantsCount,
    (select count(*) from shops) as shopsCount,
    (select count(*) from products) as productsCount
from
    dual

Answer 1

考虑dual是一个带有单行的虚拟表：

var result = new 
{ 
    RestaurantsCount = context.Restaurants.Count(),
    ShopsCount = context.Shops.Count(),
    ProductsCount = context.Products.Count()
};

单一查询解决方案：

        var result = from dummyRow in new List<string> { "X" }
                     join product in context.products on 1 equals 1 into pg
                     join shop in context.shops on 1 equals 1 into sg
                     join restaurant in context.restaurants on 1 equals 1 into rg
                     select new
                     {
                         productsCount = pg.Count(),
                         shopsCount = sg.Count(),
                         restaurantsCount = rg.Count()
                     };