前端：

1、会话列表、消息界面展示与后端打通
后端：
1、修复会话和消息服务现存问题
2、会话对象不再返回Message对象，而是使用MessageBaseDto替代
3、修改查询会话列表和会话信息的逻辑
4、新增消息列表查询
文档：
后端代码规范文档新增从数据库同步到模型的命令

backend/IM_API/Services/MessageService.cs

@@ -20,14 +20,38 @@ namespace IM_API.Services
             _mapper = mapper;
         }
 
-        public Task<List<MessageBaseDto>> GetGroupMessagesAsync(int groupId, int page, int pageSize, bool desc)
+        public async Task<List<MessageBaseDto>> GetMessagesAsync(int userId, int conversationId, int? msgId, int? pageSize, bool desc)
         {
-            throw new NotImplementedException();
-        }
-
-        public Task<List<MessageBaseDto>> GetPrivateMessagesAsync(int userAId, int userBId, int page, int pageSize, bool desc)
-        {
-            throw new NotImplementedException();
+            //获取会话信息，用于获取双方聊天的唯一标识streamkey
+            Conversation? conversation = await _context.Conversations.FirstOrDefaultAsync(
+                x => x.Id == conversationId && x.UserId == userId
+                );
+            if (conversation is null) throw new BaseException(CodeDefine.CONVERSATION_NOT_FOUND);
+            var query = _context.Messages.AsQueryable();
+            if(msgId != null)
+            {
+                query = query.Where(
+                    x => x.StreamKey == conversation.StreamKey && x.Id < msgId.Value
+                    )
+                    .OrderByDescending(x => x.Id);
+            }
+            else
+            {
+                query = query.Where(
+                    x => x.StreamKey == conversation.StreamKey && x.Id > conversation.LastReadMessageId
+                    );
+            }
+            if(pageSize != null)
+            {
+                query = query.Take(pageSize.Value);
+            }
+            var msgList = await query
+                .ToListAsync();
+            msgList = msgList
+                .OrderBy(x => x.Created)
+                .ThenBy(t => t.Id)
+                .ToList();
+            return _mapper.Map<List<MessageBaseDto>>(msgList);
         }
 
         public Task<int> GetUnreadCountAsync(int userId)