您需要在ASP.Net中查看Cascading DropDownLists的这篇文章。您将清楚如何使用ASP.NET中的多个DDlists

在ASP.Net中创建级联DropDownLists [ ^ ]

You need to see this article for Cascading DropDownLists in ASP.Net. You will clear idea how to work with Multiple DDlists in ASP.NET
Creating Cascading DropDownLists in ASP.Net[^]