KeyTrigger: KeyUp command action is not fired for the modifier keys

[pkulikov]

Summary

The following definition does not result into the invocation of a command

<b:KeyTrigger Key="LeftCtrl" FiredOn="KeyUp">
    <b:InvokeCommandAction Command="..." />
</b:KeyTrigger>

(That same behavior is for any modifier key.)

To reproduce

• Build and run the following WPF app project (.NET Framework 4.7.2): KeyTriggerDemo.zip
• Press the LEFT CTRL key several times

Expected behavior: Two lines are displayed: "UP UP UP..." and "DOWN DOWN DOWN..."
Observed behavior: No "UP"s are displayed.

Reason

The root cause is in the KeyTrigger.cs file:

XamlBehaviorsWpf/src/Microsoft.Xaml.Behaviors/Input/KeyTrigger.cs

Lines 74 to 81 in 7c79fe9

	private void OnKeyPress(object sender, KeyEventArgs e)
	{
	if (e.Key == this.Key &&
	Keyboard.Modifiers == GetActualModifiers(e.Key, this.Modifiers))
	{
	this.InvokeActions(e);
	}
	}

When the CTRL key is UP, the Keyboard.Modifiers is None (at least it has CTRL off), however GetActualModifiers returns the instance with CTRL on. Thus, the if condition returns false and actions are not invoked.

Is that by design or a bug?

[brianlagunas]

Please provide a sample application that reproduces the problem or this issue may be closed.

[pkulikov]

@brianlagunas I've uploaded the zipped project into the original post. Please check the updated post.

[montyjohn]

Has there been any outcome for this issue. It still appears to be a problem.

[zaggler]

@montyjohn @pkulikov
I've recently wrote up a work around for this issue on StackOverflow that is working. Also worth mentioning, in the work around I don't use InvokeCommandAction, I use CallMethodAction, with a few changes it should be the same.