添加项目文件。

MessageService.Domain/KeyObjects/MessageContent.cs

@@ -0,0 +1,37 @@
+using System.ComponentModel.DataAnnotations.Schema;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace MessageService.Domain.KeyObjects
+{
+    public class MessageContent
+    {
+        // 兜底文本
+        [JsonPropertyName("fallback")]
+        public string Fallback { get; init; }
+
+        // 核心 Payload，反序列化时根据外层 MessageType 转换为具体子类
+        public string RawBody { get; init; }
+        public string RawExt { get; set; } = string.Empty;
+        [JsonPropertyName("body")]
+        // 业务代码使用的对象
+        [NotMapped]
+        public object Body => string.IsNullOrEmpty(RawBody) ? null : JsonSerializer.Deserialize<object>(RawBody);
+
+        [NotMapped]
+        public Dictionary<string, string> Ext => string.IsNullOrEmpty(RawExt)
+            ? new()
+            : JsonSerializer.Deserialize<Dictionary<string, string>>(RawExt);
+
+        // 引用信息
+        [JsonPropertyName("quote")]
+        public QuoteInfo Quote { get; set; } = new();
+
+        private MessageContent() { }
+        public MessageContent(string fallback, object body)
+        {
+            Fallback = fallback;
+            RawBody = body == null ? null : JsonSerializer.Serialize(body);
+        }
+    }
+}