How can I pass the currently focused element name through a CommandParameter in XAML?

0
votes

In my WPF MVVM application I want to be able to undo changes to individual TextBox elements using the Esc key. I've set up a command for this and I want to trigger it through XAML thus:

<Window.InputBindings>
    <KeyBinding Command="{Binding EscKeyCommand}" CommandParameter="{Binding FocusManager.FocusedElement}"  Gesture="ESC" />
</Window.InputBindings>

The idea is that the CommandParameter passes the ElementName of the currently focussed TextBox (if indeed that's what's in focus) and the appropriate undo can then be handled within the ViewModel. I've tried a number of options for the CommandParameter including the one above but they all return null. So,

Question

How can I pass the currently focused element name through a CommandParameter?

2
c#wpfxamlmvvmcommandparameter
It doesn't answer the question I've specifically posed but I've just realised that I can determine the focused element name in the command using Keyboard.FocusedElement. No need therefore to pass any CommandParameter. - ifinlay
As a user, I'd be surprised if ESC was "Undo". Ctrl-Z is "undo". - Daniel Mann
Indeed, but I have surprising users ;-) - ifinlay

2 Answers

2
votes

I am glad that you have already noticed KeyBoard.FocusedElment. But there still an answer for the question. Since FocusManager.FocusedElement is an attached property, the right way to bind it should be:

CommandParameter="{Binding (FocusManager.FocusedElement), ElementName='name of the window'}"
2
votes

FocusManager gives the element with the logical focus. To use FocusManager.FocusedElement the scope needs to provided, in this case the window (this)

IInputElement focusedControl = FocusManager.GetFocusedElement(this);

But In your case since it is a text box that you need the focus of use Keyboard.FocusedElement.

In the view model when you execute EscKeyCommand get the element that has the keyboard focus with the following syntax and clear the text.

UIElement elementWithFocus = Keyboard.FocusedElement as UIElement;