diff --git a/Entity-Relationship.md b/Entity-Relationship.md
index c9f8db6..cf88b8c 100644
--- a/Entity-Relationship.md
+++ b/Entity-Relationship.md
@@ -12,6 +12,8 @@ With navigation properties, multi-table query is very convenient. Directly using
 
 [《What problems can navigation properties solve?》](https://www.cnblogs.com/kellynic/p/13575053.html)
 
+> Warm up note: to load navigation attributes, you need to solve the problem of dead cycle reference. When the reference relationship is very complex, it may lead to the failure of using navigation attributes for the first time. The second time is enough. The solution is to preheat all entity classes when the program starts, and while execute fsql.Select\<object\>().Astype (entity type);
+
 ## Custom Navigation Relationship
 
 ```csharp