后端：

新增好友请求事件和好友已添加事件

backend/IM_API/Dtos/HubResponse.cs

@@ -0,0 +1,47 @@
+using IM_API.Tools;
+
+namespace IM_API.Dtos
+{
+    public class HubResponse<T>
+    {
+        public int Code { get; init; }
+        public string Method { get; init; }
+        public HubResponseType Type { get; init; }
+        public string Message { get; init; }
+        public T? Data { get; init; }
+        public HubResponse(string method)
+        {
+            Code = CodeDefine.SUCCESS.Code;
+            Message = CodeDefine.SUCCESS.Message;
+            Type = HubResponseType.ActionStatus;
+        }
+        public HubResponse(string method,T data)
+        {
+            Code = CodeDefine.SUCCESS.Code;
+            Message = CodeDefine.SUCCESS.Message;
+            Type = HubResponseType.ActionStatus;
+            Data = data;
+        }
+        public HubResponse(CodeDefine codedefine,string method)
+        {
+            Code = codedefine.Code;
+            Method = method;
+            Message = codedefine.Message;
+            Type = HubResponseType.ActionStatus;
+        }
+        public HubResponse(CodeDefine codeDefine, string method, HubResponseType type, T? data)
+        {
+            Code = codeDefine.Code;
+            Method = method;
+            Type = type;
+            Message = codeDefine.Message;
+            Data = data;
+        }
+    }
+    public enum HubResponseType
+    {
+        ChatMsg = 1,      // 聊天内容
+        SystemNotice = 2, // 系统通知（如：申请好友成功）
+        ActionStatus = 3  // 状态变更（如：对方正在输入、已读回执）
+    }
+}

backend/IM_API/Dtos/MessageDto.cs

@@ -1,10 +1,12 @@
-namespace IM_API.Dtos
+using IM_API.Models;
+
+namespace IM_API.Dtos
 {
     public record MessageBaseDto
     {
         // 使用 { get; init; } 确保对象创建后不可修改，且支持无参构造
-        public string Type { get; init; } = default!;
-        public string ChatType { get; init; } = default!;
+        public MessageMsgType Type { get; init; } = default!;
+        public ChatType ChatType { get; init; } = default!;
         public string? MsgId { get; init; }
         public int SenderId { get; init; }
         public int ReceiverId { get; init; }