Swapping data binding in code

Question

I have two data-bound text boxes. One is bound to a string and the other to a number. The 'default' binding is set in XAML. Under some circumstances I need to reverse the bindings at runtime (the string is usually a prefix but sometimes it's a suffix). I have the following code in my view model, called when the window is loaded:

Binding stringBinding = BindingOperations.GetBinding(view.seqLeft, TextBox.TextProperty);
Binding numberBinding = BindingOperations.GetBinding(view.seqRight, TextBox.TextProperty);
view.seqLeft.SetBinding(TextBlock.TextProperty, numberBinding);
view.seqRight.SetBinding(TextBlock.TextProperty, stringBinding);

After that the code loads the properties to which the binding refers.

The problem is that the 'new' binding doesn't seem to work. What have I missed? Is there a better way?

Answer 1

I might consider exposing Prefix and Suffix strings to which View can bind, then use logic within the ViewModel, or whatever backing object you're using, to fill those strings accordingly. This option neatly segments the business concern from the visual and simplifies what you have to keep track of in your view.

Answer 2

Why monkey around with the bindings at all? If you want to have a TextBox that's bound to one of two different things, create two TextBoxes, put them in the same location, and toggle their visibility based on whatever your swap condition is.

Answer 3

The only thing wrong with my code was the Text*Block*.TextProperty in the SetBinding calls! They should, of course, have been Text*Box*.TextProperty but I'd messed with it so long I wasn't seeing the wood for the trees.