You either never assigned something to the variable, never created an instance of the value assigned to the variable, or you set the variable equal to Nothing/null manually, or you called a function that set the variable to Nothing/null for you. You don’t have to use the “new” keyword, but by default the value is Nothing/null.You would have to at least initialize to a = String. Again, this is code that C# will not compile, but VB. Same as a string, any reference type must be initialized.Empty, or to some other actual value, before it will compile in C#, or run without exception in VB. Net, set [a = “something”] before you attempt to do anything with it. Strings and some other CTS types have a misconception of being value types, like Integers, and they are not.A more complex example would be that you disposed of a class that maybe you use to access the database. But then, somewhere else, you tried to call a method of that class that used those objects that no longer exists.Other Text Box instances are updating fine and displaying in the Message Box. I've done a lot of searching and can't seem to find anything that I'm doing wrong. I have a Data Template that holds the Combo Box as well as some other Text Boxes.The Text Boxes are bound directly to properties of the Connection View Model using The Text Boxes all bind correctly, and data moves between them and the View Model with no trouble. You are correct in your assumption regarding the Phonebook Entry class.
I am currently labouring under the impression that an item bound to the child of a Data Context has that child as it's Data Context.
My specific case was a bit more complex because I was binding to the page View Model (which I didn’t want to instantiate more than once as it made web service calls) to a Combo Box in a Data Template for a cell in a Grid View.