使用 LINQ 进行多次联接

问：

我有这个疑问：

 public IQueryable<PostView> PostJoinQuery()
        {
            return _context.Posts.GroupJoin(
                _context.Users,
                post => post.User_Id,
                user => user.User_Id,
                (posts, users) => new { posts, users })
                .SelectMany(
                x => x.users.DefaultIfEmpty(),
                (post, user) => new PostView
                {
                    User_Id = post.posts.User_Id,
                    Post_Id = post.posts.Post_Id,
                    Author = user.Username,
                    First_Name = user.First_Name,
                    Last_Name = user.Last_Name,
                    Created = post.posts.Created,
                    Modified = post.posts.Modified,
                    Content = post.posts.Content,
                    Profile_Picture = user != null ? user.Profile_Picture : "No picture",
                })
                .GroupJoin(
                _context.Comments,
                post => post.Post_Id,
                comment => comment.Post_Id,
                (post, comment) => new
                {
                    PostView = post,
                    Comments = comment.Count()
                })
                .Select(result => new PostView
                {
                    User_Id = result.PostView.User_Id,
                    Post_Id = result.PostView.Post_Id,
                    Author = result.PostView.Author,
                    First_Name = result.PostView.First_Name,
                    Last_Name = result.PostView.Last_Name,
                    Created = result.PostView.Created,
                    Modified = result.PostView.Modified,
                    Content = result.PostView.Content,
                    Profile_Picture = result != null ? result.PostView.Profile_Picture : "No picture",
                    Comments = result.Comments
                });
        }

我需要在其中添加另一个 GroupJoin 与_context。图像将执行与通信相同的操作，但现在我需要它来计算图像

我尝试了以下方法：

        public IQueryable<PostView> PostJoinQuery()
        {
            return _context.Posts.GroupJoin(
                _context.Users,
                post => post.User_Id,
                user => user.User_Id,
                (posts, users) => new { posts, users })
                .SelectMany(
                x => x.users.DefaultIfEmpty(),
                (post, user) => new PostView
                {
                    User_Id = post.posts.User_Id,
                    Post_Id = post.posts.Post_Id,
                    Author = user.Username,
                    First_Name = user.First_Name,
                    Last_Name = user.Last_Name,
                    Created = post.posts.Created,
                    Modified = post.posts.Modified,
                    Content = post.posts.Content,
                    Profile_Picture = user != null ? user.Profile_Picture : "No picture",
                })
                .GroupJoin(
                _context.Comments,
                post => post.Post_Id,
                comment => comment.Post_Id,
                (post, comment) => new
                {
                    PostView = post,
                    Comments = comment.Count()
                })
                .GroupJoin(
                _context.Images,
                post => post.PostView.Post_Id,
                image => image.Post_Id,
                (post, image) => new
                {
                    PostView = post,
                    Images = image.Count()
                })
                .Select(result => new PostView
                {
                    User_Id = result.PostView.PostView.User_Id,
                    Post_Id = result.PostView.PostView.Post_Id,
                    Author = result.PostView.PostView.Author,
                    First_Name = result.PostView.PostView.First_Name,
                    Last_Name = result.PostView.PostView.Last_Name,
                    Created = result.PostView.PostView.Created,
                    Modified = result.PostView.PostView.Modified,
                    Content = result.PostView.PostView.Content,
                    Profile_Picture = result != null ? result.PostView.PostView.Profile_Picture : "No picture",
                    Comments = result.PostView.Comments,
                    Images = result.Images
                });
        }

但是我收到以下错误： 无法翻译。以可翻译的形式重写查询，或通过插入对“AsEnumerable”、“AsAsyncEnumerable”、“ToList”或“ToListAsync”的调用显式切换到客户端评估

编辑：我也试过这个，它计算图像而不是通信网络：

        public IQueryable<PostView> PostJoinQuery()
        {
            return _context.Posts.GroupJoin(
                _context.Users,
                post => post.User_Id,
                user => user.User_Id,
                (posts, users) => new { posts, users })
                .SelectMany(
                x => x.users.DefaultIfEmpty(),
                (post, user) => new PostView
                {
                    User_Id = post.posts.User_Id,
                    Post_Id = post.posts.Post_Id,
                    Author = user.Username,
                    First_Name = user.First_Name,
                    Last_Name = user.Last_Name,
                    Created = post.posts.Created,
                    Modified = post.posts.Modified,
                    Content = post.posts.Content,
                    Profile_Picture = user != null ? user.Profile_Picture : "No picture",
                })
                .GroupJoin(
                _context.Comments,
                post => post.Post_Id,
                comment => comment.Post_Id,
                (post, comments) => new
                {
                    post,
                    comments
                })
                .SelectMany(
                x => x.comments.DefaultIfEmpty(),
                (post, comments) => new PostView
                {
                    User_Id = post.post.User_Id,
                    Post_Id = post.post.Post_Id,
                    Author = post.post.Author,
                    First_Name = post.post.First_Name,
                    Last_Name = post.post.Last_Name,
                    Created = post.post.Created,
                    Modified = post.post.Modified,
                    Content = post.post.Content,
                    Profile_Picture = post.post != null ? post.post.Profile_Picture : "No picture",
                    //Comments = post.comments.Count() // *** THIS FAILS
                })
                .GroupJoin(
                _context.Images,
                post => post.Post_Id,
                image => image.Post_Id,
                (post, image) => new
                {
                    PostView = post,
                    Images = image.Count()
                })
                .Select(result => new PostView
                {
                    User_Id = result.PostView.User_Id,
                    Post_Id = result.PostView.Post_Id,
                    Author = result.PostView.Author,
                    First_Name = result.PostView.First_Name,
                    Last_Name = result.PostView.Last_Name,
                    Created = result.PostView.Created,
                    Modified = result.PostView.Modified,
                    Content = result.PostView.Content,
                    Profile_Picture = result != null ? result.PostView.Profile_Picture : "No picture",
                    Comments = result.PostView.Comments,
                    Images = result.Images
                });
        }

我需要正确计算评论数