How do I retain my private level variable in my ASP.NET control after an async postback?

Question

I am using C# and .NET 4.0.

I have an ascx control which contains two drop down lists. ddList1 is parent to ddList2 (think Car Make - Car Model). I have a constructor that populates a private variable in this control with a reference back to the original invoking object. When I do an async postback on the control (caused by changing ddList1), the private variable which was populated originally by the constructor is now null.

How do I retain the reference to the original calling object?

Thanks!

Answer 1

Store the value of the variable in your ViewState, and retrieve it during the postback. The Web is stateless: you have to work around that fact, even in WebForms.

Answer 2

使用任何状态管理技术...例如会话或隐藏字段，以在回发之间存储引用