A: 

As I see it, your cast should be: ((NIMS_Master)this.Master).MenuList

Manu
Oops, you're right. However, this is what I get when I try that:Error 6 The type or namespace name 'NIMS_Master' could not be found (are you missing a using directive or an assembly reference?) I know I'm missing something simple here to expose my NIMS_Master class to my BasePage class.
fr0man
A: 

So I had my BasePage in App_Code and was trying to set a property of my NIMS_Master class which was in the application root directory. I had to create a MasterBase class that inherits from System.Web.UI.MasterPage in App_Code and put my properties there. Sheesh, I'm not even sure why I thought I could access those class properties from within app_code.

fr0man