LINQ to Entities - Select 用户的所有好友以及他们之间的聊天

Question

如何Select当前登录用户的所有好友以及用户与好友之间的私人聊天（聊天ID）？我可以找到用户的朋友，但我也无法在他们之间聊天。

            // Select all the User's friends and the chat (Id) between them
            var friends = await _context.Friendships // Get the Friendships
                .Include(x => x.Friend).ThenInclude(x => x.ChatUsers).ThenInclude(x => x.Chat)
                .Where(x => x.Status == StatusCode.Accepted && x.ApplicationUserId == userId)
                .Select(x => x.Friend)
                .ToListAsync();

友谊table

    public class Friendship
    {
        // The primary keys/foreign keys of the associated tables
        public string ApplicationUserId { get; set; }
        public string ApplicationFriendUserId { get; set; }

        // Reference to the user that has the friend
        public User ApplicationUser { get; set; }

        // Reference to the friend
        public User Friend { get; set; }

        // The status of the friendship
        public StatusCode Status { get; set; }
    }

用户table

    public class User : IdentityUser
    {
        // Reference to all user's chats
        public ICollection<ChatUser> ChatUsers { get; set; }

        // Reference to all the user's friendships
        public ICollection<Friendship> UsersFriendships { get; set; }

        // Reference to all the friend's friendships (their point of view)
        public ICollection<Friendship> FriendsFriendships { get; set; }
    }

聊天用户table

    public class ChatUser
    {
        // The primary key/foreign keys of the associated tables
        public int ChatId { get; set; }
        public string UserId { get; set; }

        // The role that the User can be
        public UserRole Role { get; set; }

        // Reference to the chat
        public Chat Chat { get; set; }

        // Reference to the user
        public User User { get; set; }
    }

聊天

    
    public class Chat
    {
        // The primary key
        public int Id { get; set; }

        // The chat's name
        public string Name { get; set; }

        // The chat type, e.g room, private
        public ChatType Type { get; set; }

        // Reference to all the Chat's Users
        public ICollection<ChatUser> ChatUsers { get; set; }
    }

谢谢

Answer 1

这个查询：

var friends = await _context.Friendships // Get the Friendships
    .Include(x => x.Friend).ThenInclude(x => x.ChatUsers).ThenInclude(x => x.Chat)
    .Where(x => x.Status == StatusCode.Accepted && x.ApplicationUserId == userId)
    .Select(x => x.Friend)
    .ToListAsync();

...加载用户朋友与朋友相应的聊天，其中包括不与当前用户的聊天。

有了用于聊天和友谊的域结构，尝试 link 以有意义的方式建立它们看起来相当棘手。使用简单的两遍方法很可能：

var friendIds = _context.Users
    .Where(x => s.UserId == userId)
    .SelectMany(x => x.UsersFriendships.Where(f => f.Status == StatusCode.Accepted).Select(f => f.ApplicationFriendUserId))
    .ToList(); // Get all accepted Friend IDs.


 var chats = _context.Chats
     .Where(x => x.ChatUsers.Any(cu => cu.UserId) && x => x.ChatUsers.Any(cu => friendIds.Contains(cu.UserId)
     .Select(x => new 
     {
         Chat = x,
         Friends = x.ChatUsers.Where(cu => friendIds.Contains(cu.UserId)).Select(cu => cu.User).ToList()
      }).ToList();

聊天与两个或更多用户相关，与 restricted/linked 友谊无关。

Joe 可以与 Sam、Jane 和 John 成为朋友，并进行以下聊天：

聊天 1：乔 <-> 山姆

聊天 2：乔 <-> 简

聊天 3：乔 <-> 简 <-> 山姆

聊天 4：乔 <-> 弗兰克

聊天 5：乔 <-> 弗兰克 <-> 萨姆

我们想要聊天 1、2、3 和 5 returned。没有与 John 的聊天，我们不关心与 Frank 的聊天，但确实关心与 Frank 和 Sam 的聊天，因为 Sam 是朋友。目标是确定 Joe 正在与他的一个或多个朋友进行哪些聊天。对于每场比赛，我们 return 聊天以及当前也在该聊天中的任何朋友。

两次传递方法的警告是，它假设朋友列表将保持相当小，不会大到超过为获得匹配聊天而生成的 IN() 列表。

LINQ to Entities - Select 用户的所有好友以及他们之间的聊天

LINQ to Entities - Select all the User's friends and the Chat between them

linq-to-entities

entity-framework

asp.net-core-mvc

.net-core

asp.net-core