C# Lambda查询转换。按选择行计数（EF6代码优先）

我有两张简单的桌子

波斯特是大师，拥有n张选票。我想返回他们的选票计数职位。 这是我的代码：

db.posts.Select(p=>
new PostlDto{Title= p.Title, VoteCount= p.Votes.Count})

我可以打一个电话来获取帖子，打几个电话来获取计数。 但问题是每次它都选择行，而不是对行进行计数，这是一个耗时的操作。 这就是sql分析器向我展示的内容

exec sp_executesql N'SELECT 
    [Extent1].[Id] AS [Id], 
    [Extent1].[PostId] AS [PostId], 
    FROM [dbo].[Votes] AS [Extent1]
    WHERE [Extent1].[PostId] = @EntityKeyValue1',N'@EntityKeyValue1 int',@EntityKeyValue1=6

我还尝试通过在基本查询中包含投票表来执行count 1调用，但也花费了太长时间，因为它还返回行而不是count|

 db.posts
.Include(p=>p.Votes)
.Select(p=>
 new PostlDto{Title= p.Title, VoteCount= p.Votes.Count})

这就是它转换为的查询

SELECT 
    [Project1].[Id] AS [Id], 
    [Project1].[Title] AS [Title], 
    [Project1].[C1] AS [C1], 
    [Project1].[Id1] AS [Id1], 
    [Project1].[Pid] AS [Pid], 
    [Project1].[PostId] AS [PostId], 
    FROM ( SELECT 
        [Extent1].[Id] AS [Id], 
        [Extent1].[Title] AS [Title], 
        [Extent2].[Id] AS [Id1], 
        [Extent2].[PostId] AS [PostId], 
        CASE WHEN ([Extent2].[Id] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C1]
        FROM  [dbo].[Posts] AS [Extent1]
        LEFT OUTER JOIN [dbo].[Votes] AS [Extent2] ON [Extent1].[Id] = [Extent2].[PostId]
    )  AS [Project1]
    ORDER BY [Project1].[Id] ASC, [Project1].[C1] ASC

如何将其改为运行简单计数|

---

运行这些查询需要几秒钟

一定还有别的事。将您的代码与此非复制代码进行比较：

using System;
using System.Linq;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Data.Entity;
using System.Data;
using System.Diagnostics;

namespace Ef6Test
{

    public class Post
    {
        public int Id { get; set; }
        public string Title { get; set; }
        public virtual ICollection<Vote> Votes { get; } = new HashSet<Vote>();
    }
    public class Vote
    {
        public int Id { get; set; }
        public Post Post { get; set; }

    }

    public class PostDto
    {
        public string Title { get; set; }
        public int VoteCount { get; set; }
    }
    class Db : DbContext
    {


        public DbSet<Post> Posts { get; set; }
        public DbSet<Vote> Votes { get; set; }
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
        }




    }

    class Program
    {


        static void Main(string[] args)
        {



            Database.SetInitializer(new DropCreateDatabaseAlways<Db>());


            using (var db = new Db())
            {
                db.Database.Log = m => Console.WriteLine(m);
                db.Database.Initialize(false);

                var posts = db.Posts.Select(p => new PostDto { Title = p.Title, VoteCount = p.Votes.Count }).ToList();



            }

            Console.WriteLine("Hit any key to exit");
            Console.ReadKey();
        }
    }
}

---

这个问题很愚蠢！我有一个方法，我用它将我的对象转换成DTO，比如.select（convert），这是一个非常简单的方法。这就是EF变傻的原因！：\请不要把问题的答案加上去。@CodyGray，好的，那么把它放在哪里呢？大卫已经回答了。你已经在大卫的回答下发表了评论。您可以建议进行编辑，以使实际解决方案更加清晰。为了使编辑获得批准，您需要编写一份非常清晰的编辑摘要。@CodyGray ok，Cool:）

SELECT
    [Extent1].[Id] AS [Id],
    [Extent1].[Title] AS [Title],
    (SELECT
        COUNT(1) AS [A1]
        FROM [dbo].[Votes] AS [Extent2]
        WHERE [Extent1].[Id] = [Extent2].[Post_Id]) AS [C1]
    FROM [dbo].[Posts] AS [Extent1]