前端：

增加会话缓存
后端：
增加触发消息创建事件
增加消息创建事件触发后的处理函数

backend/IM_API/Application/EventHandlers/ConversationEventHandler.cs

@@ -30,58 +30,26 @@ namespace IM_API.Application.EventHandlers
             _context = imContext;
             _mapper = mapper;
         }
-
-        /*
-         * 此方法有并发问题，当双方同时第一次发送消息时，
-         * 会出现同时创建的情况，其中一方会报错，
-         * 导致也未走到更新逻辑，会话丢失
-         */
         public async Task Handle(MessageCreatedEvent @event)
         {
-            //此处仅处理私聊会话创建
+            if(@event.ChatType == ChatType.PRIVATE)
-            if (@event.ChatType == ChatType.GROUP)
             {
-                return;
+                Conversation? userAConversation = await _context.Conversations.FirstOrDefaultAsync(
-            }
+                    x => x.UserId == @event.MsgSenderId && x.TargetId == @event.MsgRecipientId
-            var conversation = await _context.Conversations.FirstOrDefaultAsync(
+                    );
-                   x => x.UserId == @event.MsgSenderId && x.TargetId == @event.MsgRecipientId
+                Conversation? userBConversation = await _context.Conversations.FirstOrDefaultAsync(
-                );
+                    x => x.UserId == @event.MsgRecipientId && x.TargetId == @event.MsgSenderId
-            //如果首次发消息则创建双方会话
+                    );
-            if (conversation is null)
+                if(userAConversation is null || userBConversation is null)
-            {
-                Conversation senderCon = _mapper.Map<Conversation>(@event);
-                Conversation ReceptCon = _mapper.Map<Conversation>(@event);
-                ReceptCon.UserId = @event.MsgRecipientId;
-                ReceptCon.TargetId = @event.MsgSenderId;
-                ReceptCon.UnreadCount += 1;
-                ReceptCon.LastReadMessageId = null;
-                _context.Conversations.AddRange(senderCon,ReceptCon);
-                await _context.SaveChangesAsync();
-            }
-            else
-            {
-                Conversation senderCon = conversation;
-                Conversation? ReceptCon = await _context.Conversations.FirstOrDefaultAsync(
-                    x => x.UserId == @event.MsgRecipientId && x.TargetId == @event.MsgSenderId);
-                if (ReceptCon is null)
                 {
-                    _logger.LogError("ConversationEventHandlerError：接收者会话对象缺失！Event:{Event}", JsonConvert.SerializeObject(@event));
+                    _logger.LogError("消息事件更新会话信息失败：{@event}",@event);
-                    throw new BaseException(CodeDefine.SYSTEM_ERROR);
                 }
-
+                userAConversation.LastMessage = @event.MessageContent;
-                //更新发送者conversation
+                userAConversation.LastReadMessageId = @event.MessageId;
-                senderCon.UnreadCount = 0;
+                userBConversation.LastMessage = @event.MessageContent;
-                senderCon.LastReadMessageId = @event.MessageId;
+                userBConversation.UnreadCount += 1;
-                senderCon.LastMessage = @event.MessageContent;
+                _context.UpdateRange(userAConversation,userBConversation);
-                senderCon.LastMessageTime = DateTime.Now;
-                //更新接收者conversation
-                ReceptCon.UnreadCount += 1;
-                ReceptCon.LastMessage = @event.MessageContent;
-                senderCon.LastMessageTime = DateTime.Now;
-                _context.Conversations.UpdateRange(senderCon, ReceptCon);
                 await _context.SaveChangesAsync();
-
-
             }
         }
     }

backend/IM_API/Application/EventHandlers/SignalREventHandler.cs

@@ -1,6 +1,9 @@
-using IM_API.Application.Interfaces;
+using AutoMapper;
+using IM_API.Application.Interfaces;
 using IM_API.Domain.Events;
+using IM_API.Dtos;
 using IM_API.Hubs;
+using IM_API.Models;
 using IM_API.Tools;
 using Microsoft.AspNetCore.SignalR;
 
@@ -9,15 +12,20 @@ namespace IM_API.Application.EventHandlers
     public class SignalREventHandler : IEventHandler<MessageCreatedEvent>
     {
         private readonly IHubContext<ChatHub> _hub;
-        public SignalREventHandler(IHubContext<ChatHub> hub)
+        private readonly IMapper _mapper;
+        public SignalREventHandler(IHubContext<ChatHub> hub, IMapper mapper)
         {
             _hub = hub;
+            _mapper = mapper;
         }
 
         public async Task Handle(MessageCreatedEvent @event)
         {
-            var streamKey = @event.StreamKey;
+            if(@event.ChatType == Models.ChatType.PRIVATE)
-            await _hub.Clients.Group(streamKey).SendAsync(SignalRMethodDefine.ReceiveMessage, @event);
+            {
+                MessageBaseDto messageBaseDto = _mapper.Map<MessageBaseDto>(_mapper.Map<Message>(@event));
+                await _hub.Clients.Users(@event.MsgRecipientId.ToString()).SendAsync("ReceiveMessage", messageBaseDto);
+            }
         }
     }
 }

backend/IM_API/Hubs/ChatHub.cs

@@ -1,4 +1,7 @@
-using IM_API.Dtos;
+using AutoMapper;
+using IM_API.Application.Interfaces;
+using IM_API.Domain.Events;
+using IM_API.Dtos;
 using IM_API.Interface.Services;
 using IM_API.Models;
 using IM_API.Tools;
@@ -11,10 +14,14 @@ namespace IM_API.Hubs
     {
         private IMessageSevice _messageService;
         private readonly IConversationService _conversationService;
-        public ChatHub(IMessageSevice messageService, IConversationService conversationService)
+        private readonly IEventBus _eventBus;
+        private readonly IMapper _mapper;
+        public ChatHub(IMessageSevice messageService, IConversationService conversationService, IEventBus eventBus, IMapper mapper)
         {
             _messageService = messageService;
             _conversationService = conversationService;
+            _eventBus = eventBus;
+            _mapper = mapper;
         }
 
         public async override Task OnConnectedAsync()
@@ -51,8 +58,6 @@ namespace IM_API.Hubs
             {
                 msgInfo = await _messageService.SendGroupMessageAsync(int.Parse(userIdStr), dto.ReceiverId, dto);
             }
-
-                await Clients.Users(dto.ReceiverId.ToString()).SendAsync("ReceiveMessage", msgInfo);
             return;
         }
     }

backend/IM_API/Services/MessageService.cs

@@ -1,4 +1,6 @@
 using AutoMapper;
+using IM_API.Application.Interfaces;
+using IM_API.Domain.Events;
 using IM_API.Dtos;
 using IM_API.Exceptions;
 using IM_API.Interface.Services;
@@ -13,11 +15,13 @@ namespace IM_API.Services
         private readonly ImContext _context;
         private readonly ILogger<MessageService> _logger;
         private readonly IMapper _mapper;
-        public MessageService(ImContext context, ILogger<MessageService> logger, IMapper mapper)
+        private readonly IEventBus _eventBus;
+        public MessageService(ImContext context, ILogger<MessageService> logger, IMapper mapper, IEventBus eventBus)
         {
             _context = context;
             _logger = logger;
             _mapper = mapper;
+            _eventBus = eventBus;
         }
 
         public async Task<List<MessageBaseDto>> GetMessagesAsync(int userId, int conversationId, int? msgId, int? pageSize, bool desc)
@@ -92,6 +96,7 @@ namespace IM_API.Services
             message.StreamKey = StreamKeyBuilder.Group(groupId);
             _context.Messages.Add(message);
             await _context.SaveChangesAsync();
+            await _eventBus.PublishAsync(_mapper.Map<MessageCreatedEvent>(message));
             return _mapper.Map<MessageBaseDto>(message);
 
         }
@@ -107,6 +112,7 @@ namespace IM_API.Services
             message.StreamKey = StreamKeyBuilder.Private(dto.SenderId, dto.ReceiverId);
             _context.Messages.Add(message);
             await _context.SaveChangesAsync();
+            await _eventBus.PublishAsync(_mapper.Map<MessageCreatedEvent>(message));
             return _mapper.Map<MessageBaseDto>(message);
         }
         #endregion

frontend/web/src/stores/chat.js

@@ -24,7 +24,6 @@ export const useChatStore = defineStore('chat', {
             this.messages = [];
             //先从浏览器缓存加载一部分消息列表
             const localHistory = await messagesDb.getPageMessages(sessionId, new Date().toISOString(), this.pageSize);
-            console.log(localHistory)
             if (localHistory.length > 0) {
                 this.messages = localHistory;
             } else {

frontend/web/src/stores/conversation.js

@@ -0,0 +1,63 @@
+import { defineStore } from "pinia";
+import { messageService } from "@/services/message";
+import { conversationDb } from "@/utils/db/conversationDB";
+import { useMessage } from "@/components/messages/useAlert";
+
+const message = useMessage();
+
+export const useConversationStore = defineStore('conversation', {
+    state: () => ({
+        conversations: []
+    }),
+    actions: {
+        async addConversation(conversation) {
+            await conversationDb.save(conversation);
+            this.conversations.unshift(conversation)
+        },
+        /**
+         * 加载当前会话消息列表 
+         */
+        async loadUserConversations() {
+            if (this.conversations.length == 0) {
+                try {
+                    const covnersationsCache = await conversationDb.getAll();
+                    if (covnersationsCache && covnersationsCache.length > 0) {
+                        covnersationsCache.sort((a, b) => {
+                            return new Date(a.dateTime) - new Date(b.dateTime);
+                        })
+                    }
+                } catch (e) {
+                    message.error('读取本地会话缓存失败...');
+                    console.log('读取本地会话缓存失败：', e);
+                }
+            }
+            await this.fetchConversationsFromServier()
+        },
+        /**
+         * 从服务器加载新消息
+         * @param {*} sessionId 
+         * @returns 
+         */
+        async fetchConversationsFromServier() {
+            const newConversations = (await messageService.getConversations()).data;
+            if (newConversations.length > 0) {
+                // 1. 将当前的本地数据转为 Map，方便通过 ID 快速查找 (O(1) 复杂度)
+                const localMap = new Map(this.conversations.map(item => [item.id, item]));
+                newConversations.forEach(item => {
+                    const existingItem = localMap.get(item.id);
+                    if (existingItem) {
+                        // --- 局部更新 ---
+                        // 使用 Object.assign 将新数据合并到旧对象上，保持响应式引用
+                        Object.assign(existingItem, item);
+                    } else {
+                        // --- 插入新会话 ---
+                        this.conversations.unshift(item);
+                    }
+                    // 同步到本地数据库
+                    conversationDb.save(item);
+                });
+
+            }
+        }
+    }
+})

frontend/web/src/utils/db/baseDb.js

@@ -0,0 +1,19 @@
+import { openDB } from "idb";
+
+const DBNAME = 'IM_DB';
+const STORE_NAME = 'messages';
+const CONVERSARION_STORE_NAME = 'conversations';
+
+export const dbPromise = openDB(DBNAME, 2, {
+    upgrade(db) {
+        if (!db.objectStoreNames.contains(STORE_NAME)) {
+            const store = db.createObjectStore(STORE_NAME, { keyPath: 'msgId' });
+            store.createIndex('by-sessionId', 'sessionId');
+            store.createIndex('by-time', 'timeStamp');
+        }
+        if (!db.objectStoreNames.contains(CONVERSARION_STORE_NAME)) {
+            const store = db.createObjectStore(CONVERSARION_STORE_NAME, { keyPath: 'id' });
+            store.createIndex('by-id', 'id');
+        }
+    }
+})

frontend/web/src/utils/db/conversationDB.js

@@ -0,0 +1,18 @@
+import { dbPromise } from "./baseDb";
+
+const STORE_NAME = 'conversations';
+
+export const conversationDb = {
+    async save(conversation) {
+        (await dbPromise).put(STORE_NAME, conversation);
+    },
+    async getById(id) {
+        return (await dbPromise).getFromIndex(STORE_NAME, 'by-id', id);
+    },
+    async getAll() {
+        return (await dbPromise).getAll(STORE_NAME);
+    },
+    async clearAll() {
+        (await dbPromise).clear(STORE_NAME);
+    }
+}

frontend/web/src/utils/db/messageDB.js

@@ -1,18 +1,7 @@
-import { openDB } from "idb";
+import { dbPromise } from "./baseDb";
 
-const DBNAME = 'IM_DB';
 const STORE_NAME = 'messages';
 
-export const dbPromise = openDB(DBNAME, 1, {
-    upgrade(db) {
-        if (!db.objectStoreNames.contains(STORE_NAME)) {
-            const store = db.createObjectStore(STORE_NAME, { keyPath: 'msgId' });
-            store.createIndex('by-sessionId', 'sessionId');
-            store.createIndex('by-time', 'timeStamp');
-        }
-    }
-})
-
 export const messagesDb = {
     async save(msg) {
         return (await dbPromise).put(STORE_NAME, msg);

frontend/web/src/views/messages/MessageContent.vue

@@ -50,6 +50,7 @@ import { formatDate } from '@/utils/formatDate';
 import { useChatStore } from '@/stores/chat';
 import { generateSessionId } from '@/utils/sessionIdTools';
 import { useSignalRStore } from '@/stores/signalr';
+import { useConversationStore } from '@/stores/conversation';
 
 const props = defineProps({
     id:{
@@ -60,6 +61,7 @@ const props = defineProps({
 
 const chatStore = useChatStore();
 const signalRStore = useSignalRStore();
+const conversationStore = useConversationStore();
 
 const input = ref('');   // 输入框内容
 const historyRef = ref(null); // 绑定 DOM 用于滚动
@@ -118,20 +120,20 @@ function toggleEmoji() {
 }
 
 async function loadConversation(conversationId) {
+  /*
   const res = await messageService.getConversationById(conversationId);
   conversationInfo.value = res.data;
-  console.log(res)
+  */
-}
+ if(conversationStore.conversations.length == 0){
-
+  await conversationStore.loadUserConversations();
-async function loadMessages(conversationId, msgId = null, pageSize = null) {
+ }
-  const res = await messageService.getMessages(conversationId);
+ conversationInfo.value = conversationStore.conversations.find(x => x.id == Number(conversationId));
-  messages.value = res.data;
 }
 
 // 初始化时滚动到底部
 onMounted(async () => {
   await loadConversation(props.id);
-  const sessionid = generateSessionId(conversationInfo.userId, conversationInfo.targetId)
+  const sessionid = generateSessionId(conversationInfo.value.userId, conversationInfo.value.targetId)
   await chatStore.swtichSession(sessionid,props.id);
   scrollToBottom();
 });

frontend/web/src/views/messages/MessageList.vue

@@ -13,7 +13,7 @@
              class="list-item" :class="{active: activeId === s.id}" @click="selectSession(s)">
           <div class="avatar-container">
             <img :src="s.targetAvatar ?? defaultAvatar" class="avatar-std" />
-            <span v-if="s.unread > 0" class="unread-badge">{{ s.unreadCount ?? 0 }}</span>
+            <span v-if="s.unreadCount > 0" class="unread-badge">{{ s.unreadCount ?? 0 }}</span>
           </div>
           <div class="info">
             <div class="name-row">
@@ -36,26 +36,19 @@ import { ref, computed, nextTick, onMounted } from 'vue'
 import { messageService } from '@/services/message'
 import defaultAvatar from '@/assets/default_avatar.png'
 import { formatDate } from '@/utils/formatDate'
+import { useConversationStore } from '@/stores/conversation'
+
+const conversationStore = useConversationStore();
 
 const searchQuery = ref('')
-const input = ref('')
-const historyRef = ref(null)
 const activeId = ref(1)
 const conversations = ref([]);
 
-const filteredSessions = computed(() => conversations.value.filter(s => s.targetName.includes(searchQuery.value)))
+const filteredSessions = computed(() => conversationStore.conversations.filter(s => s.targetName.includes(searchQuery.value)))
-
-const currentSession = computed(() => sessions.value.find(s => s.id === activeId.value))
 
 function selectSession(s) {
   activeId.value = s.id
   router.push(`/messages/chat/${s.id}`)
-  scrollToBottom()
-}
-
-const scrollToBottom = async () => {
-  await nextTick()
-  if (historyRef.value) historyRef.value.scrollTop = historyRef.value.scrollHeight
 }
 
 async function loadConversation() {
@@ -65,7 +58,7 @@ async function loadConversation() {
 }
 
 onMounted(async () => {
-  await loadConversation();
+  await conversationStore.loadUserConversations();
 })