diff --git a/PEIS/Entity/DictHazardTypecs.cs b/PEIS/Entity/DictHazardTypecs.cs
index 615aa71..5156085 100644
--- a/PEIS/Entity/DictHazardTypecs.cs
+++ b/PEIS/Entity/DictHazardTypecs.cs
@@ -15,7 +15,7 @@ namespace PEIS.Entity
         /// <summary>
         /// ParentID
         /// </summary>
-        public Int64 ParentID { get; set; }
+        public Int64? ParentID { get; set; }
         /// <summary>
         /// 名字
         /// </summary>