LINQ-嵌套查询 [英] LINQ - Nested Query

问题描述

我有一个SQL语句，试图将其转换为LINQ查询.我需要这样做是因为我无法编辑数据库:(.无论如何，我都有一个如下所示的SQL语句:

I have a SQL Statement that I am trying to convert to a LINQ query. I need to do this because I can't edit my database :(. Regardless, I have a SQL Statement that looks like the following:

SELECT
  CustomerID,
  FirstName,
  LastName,
  Gender,
  BirthMonth,
  (SELECT COUNT(ID) FROM PurchaseOrder WHERE [CustomerID]=CustomerID) as TotalPurchases
FROM
  MyEntities

除了嵌套查询部分，我知道如何在LINQ中执行所有操作.目前，我有以下内容:

I know how to do everything in LINQ excepted for the nested query part. Currently, I have the following:

var results = from x in context.MyEntities 
              select new Customer() 
              { 
                CustomerID = x.CustomerID, 
                FirstName = x.FirstName, 
                LastName = x.LastName, 
                Gender = x.Gender, 
                BirthMonth = x.BirthMonth,
                TotalPurchases = ? 
              };

如何在LINQ中执行嵌套查询以获取TotalPurchases的值?

How do I execute a nested query in LINQ to get the value for TotalPurchases?

非常感谢您！

推荐答案

您也可以将Linq to Entities查询嵌套:

You can just nest the Linq to Entities query as well:

var results = from x in context.MyEntities 
              select new Customer() 
              { 
                CustomerID = x.CustomerID, 
                FirstName = x.FirstName, 
                LastName = x.LastName, 
                Gender = x.Gender, 
                BirthMonth = x.BirthMonth,
                TotalPurchases = context.PurchaseOrders
                                        .Where(po=>po.CustomerId == x.CustomerId)
                                        .Count()
              };

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