如何使用计数相关联的实体凡在实体框架

Question

我有这样的：

 var queryResult = (from post in posts 
        select new 
           { 
            post, 
            post.Author, 
            post.Tags, 
            post.Categories, 
            Count = post.Comments.Count() 
           }).ToList(); 

但我需要的东西是这样的：

 var queryResult = (from post in posts 
        select new 
           { 
            post, 
            post.Author, 
            post.Tags, 
            post.Categories, 
            Count = post.Comments.Where(x=>x.IsPublic).Count() 
           }).ToList(); 

但post.Comments是一个ICollection的

Answer 1

这工作：

 var queryResult = (from post in posts 
          join comment in comments.Where(x=> x.IsPublic) on post.Id equals comment.Post.Id into g 
        select new 
           { 
            post, 
            post.Author, 
            post.Tags, 
            post.Categories, 
            Count = g.Count() 
           }) 

但在所有的解决方案，我们有这个问题How to use Include and Anonymous Type in same query in Entity Framework?

Answer 2

如何关于使用Enumerable.Cast<T>()这样？

var queryResult = (from post in posts 
        select new 
           { 
            post, 
            post.Author, 
            post.Tags, 
            post.Categories, 
            Count = post.Comments.Cast<Comment>() 
                 .Where(x=>x.IsPublic).Count() 
           }).ToList(); 

假设post.Comments类型为Comment

Answer 3

尝试：

var queryResult = (from post in context.Posts 
       select new 
          { 
           post, 
           post.Author, 
           post.Tags, 
           post.Categories, 
           Count = context.Comments.Where(c => c.Post == post).Where(c => IsPublic == 1).Count() 
          }).ToList(); 

Answer 4

我写它作为LukLed没有，但要使它工作，我将使用后的实体的PK：

var queryResult = (from post in context.Posts 
       select new 
          { 
           post, 
           post.Author, 
           post.Tags, 
           post.Categories, 
           Count = context.Comments.Where(c => c.Post.Id == post.Id && c.IsPublic == 1).Count() 
          }).ToList(); 

或者，如果forign键通过关联暴露Post.Id可能只是被写成帖子ID我相信它会更有效率。