你没有在 UpdatePanel [ ^ ]应该触发部分回发，因此DDL的AutoPostBack = true将启动整页发布...

使用 ChildrenAsTriggers [ ^ ]属性，或使用触发器 [ ^ ]声明...

You didn't declared when UpdatePanel[^] should trigger a partial post back, so the AutoPostBack=true of the DDL will initiate full page post...
Use ChildrenAsTriggers[^] property of UpdatePanel, or use Triggers[^] declaration...

如果没有必要，请删除更新面板。

Please remove update panel if it is not necessary.