修复您的代码.您还可以从模糊的描述中得到什么其他答案?如果您需要更多信息，请尝试发布一些代码.您是否尝试过设置断点以查看执行操作时所调用的代码?无疑，更改下拉列表选择的事件处理程序中的代码是导致此问题的原因.

Fix your code. What other answer could you expect from a vague description ? If you want more info, try posting some code. Have you tried setting breakpoints to see what code is called when you do what you''re doing ? Code in the event handler for the droplist selection changed is most certainly the cause of hte issue.