Chapter 8 User Controls: Try It Out Pages 283-286

epc · October 11th, 2009, 11:41 AM

For some reason I struggle with wrapping my head around a few concepts related to User Control coding. Particularily the Try It Out on pages 283-286. When I set NavigateURL for banner1 in the Code Behind of the AboutUs page why does this code not affect lnkVertical NavigateURL settings for the control on the MasterPage. My first thought is that the AboutUs.aspx viewstate relates only to the banner1 control defined there, but why does the NavigateURL code not affect the viewstate of the MasterPage sidebar user control settings.

Imar · October 11th, 2009, 11:53 AM

Hi there,

Each loaded User Control maintains its own state. As you've seen, ViewState contains the (encoded) values that are set by .NET or by your own code. However, it doesn't directly write to the __ViewState hidden field but writes and reads through the StateBag class. Internally, this class keeps track of which value belongs to which control instance. So, rather than storing with the following pseude code:

Banner.NavigateUrl = SomeValue

it does something like:

Parent + Banner.ID + NavigateUrl = SomeValue

This means the NavigateUrl can be stored in ViewState seperately for each Banner control you have somewhere in the Page hierarchy (e.g. in a master Page, a Page, a User Contro, and so on), even if they have the same ID (since they are located somewhere in the hierarchy, the "path" to them / their parent is unique.

Does this help?

Imar