后端：

新增好友请求事件和好友已添加事件

backend/IM_API/Program.cs

@@ -9,6 +9,8 @@ using Microsoft.EntityFrameworkCore;
 using Microsoft.IdentityModel.Tokens;
 using StackExchange.Redis;
 using System.Text;
+using System.Text.Json;
+using System.Text.Json.Serialization;
 
 namespace IM_API
 {
@@ -38,7 +40,12 @@ namespace IM_API
             
             builder.Services.AddAllService(configuration);
 
-            builder.Services.AddSignalR();
+            builder.Services.AddSignalR().AddJsonProtocol(options =>
+            {
+                // 枚举输出字符串
+                options.PayloadSerializerOptions.Converters.Add(new JsonStringEnumConverter());
+                options.PayloadSerializerOptions.PropertyNamingPolicy = JsonNamingPolicy.CamelCase;
+            });
             //允许所有来源（跨域）
             builder.Services.AddCors(options =>
             {
@@ -110,6 +117,10 @@ namespace IM_API
             {
                 // 保持 ISO 8601 格式
                 options.JsonSerializerOptions.Converters.Add(new UtcDateTimeConverter());
+                // 将枚举转换为字符串
+                options.JsonSerializerOptions.Converters.Add(new JsonStringEnumConverter());
+                // 建议：保持驼峰命名
+                options.JsonSerializerOptions.PropertyNamingPolicy = JsonNamingPolicy.CamelCase;
             });
             builder.Services.AddModelValidation(configuration);
             // Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle