Another WPF question for you all.
I have a user control that contains a text box and button. The button opens a “folder selection” dialog; when the user selects a folder, the text box should populate with the path the user selected. That works fine.
Inside of the user control, I have a dependency property named Path. When the user makes their selection, the Path gets updated and the text box bound to it also updates. That works great.
Now, the parent View also needs to know what this Path value is. What to do from here?
I’d assume that we should add a property to the parent’s view model named Path. Easy enough — then what do we bind it to? The Path dependency property of the user control? Can that be bound to both the parent’s View Model and user control’s text box simultaneously?
I tried adding the user controls attributes without success:
<v:MyControl Path="{Binding ViewModels:MyViewModel.Path}" ... />
No errors, it just didn’t update the view model. If this approach is feasible, I can post more of the code.
Dependency properties can be the source of multiple bindings, yes. Speaking solely about the view, I could have a master slider with five text boxes bound to its value, and that would work just fine.
However, since you’re living in MVVM, it’s probably more sound to use the view model’s change-notifying properties as the Single Source Of Truth for this screen. The user control writes to this property, and the parent view reads from it, simple as that.
Rule of thumb: if more than one view-level component needs access to a property, bind both of them to the view model, not to each other.