add:

更新

backend/IM_API/Dtos/CreateUploadTaskDto.cs

@@ -0,0 +1,10 @@
+namespace IM_API.Dtos
+{
+    public class CreateUploadTaskDto
+    {
+        public string FileName { get; set; } = default!;
+        public long FileSize { get; set; }
+        public string ContentType { get; set; } = default!;
+        public string FileHash { get; set; } = default!; 
+    }
+}

backend/IM_API/Dtos/Message/MessagTypeDto.cs

@@ -0,0 +1,26 @@
+namespace IM_API.Dtos.Message
+{
+    public class RequestMessageType
+    {
+        public Guid FileId { get; set; }
+        public long Size { get; set; }
+    }
+    public class BaseMessageType: RequestMessageType
+    {
+        public string Url { get; set; }
+        public string Provider { get; set; }
+        public string Format { get; set; }
+        public string Text { get; set; }
+    }
+    public class ImageDto() : BaseMessageType
+    {
+        public string Thumb { get; set; }
+        public int W { get; set; }
+        public int H { get; set; }
+    }
+
+    public class VideoDto() : ImageDto
+    {
+        public int Duration { get; set; }
+    }
+}

backend/IM_API/Dtos/MessageDto.cs

@@ -10,7 +10,7 @@ namespace IM_API.Dtos
         public Guid MsgId { get; init; }
         public int SenderId { get; init; }
         public int ReceiverId { get; init; }
-        public string Content { get; init; } = default!;
+        public string Content { get; set; } = default!;
         public DateTimeOffset TimeStamp { get; init; }
         public MessageBaseDto() { }
     }

backend/IM_API/Dtos/UploadPartDto.cs

@@ -0,0 +1,8 @@
+namespace IM_API.Dtos
+{
+    public class UploadPartDto
+    {
+        public int PartNumber { get; set; }
+        public string? ETag { get; set; }
+    }
+}