diff --git a/CalendarNotepad/Models/PlusFileUnit.cs b/CalendarNotepad/Models/PlusFileUnit.cs
index 6432684..c4f2781 100644
--- a/CalendarNotepad/Models/PlusFileUnit.cs
+++ b/CalendarNotepad/Models/PlusFileUnit.cs
@@ -1,4 +1,6 @@
-namespace CalendarNotepad.Models
+using System.ComponentModel.DataAnnotations;
+
+namespace CalendarNotepad.Models
 {
     /// <summary>
     /// 附件文件单元
@@ -8,6 +10,7 @@
         /// <summary>
         /// 文件指纹ID
         /// </summary>
+        [Key]
         public string? FileId { get; set; }
         /// <summary>
         /// 文件内容