CommandParameter invalidates CanExecute

[miloush]

Fixes Issue #3452 #4078 (also discussed in #316)

In summary, the issue is that

<MenuItem CommandParameter="P" Command="C" />

and

<MenuItem Command="C" CommandParameter="P" />

behave differently. In the latter case, C.CanExecute is called to determine whether the element should be enabled, but since the parameter has not been parsed yet, CanExecute is called with a null argument. After the parameter is parsed, the status of the command is not re-evaluated and therefore the element stays disabled when it shouldn't be.

A common workaround is to use the former syntax.

Description

Adds property changed callback to CommandParameterProperty wherever applicable (MenuItem, ButtonBase, Hyperlink, RibbonGallery, RibbonTextBox) to call UpdateCanExecute.

This way, changing command parameter makes it re-evaluate command's CanExecute value. Most notably, this will make the order of Command and CommandParameter properties in XAML irrelevant.

Note that ThumbButtonInfo already implements this behaviour.

Customer Impact

Not taking this fix retains the existing XAML attributes order significance (and the inconsistency with ThumbButtonInfo behaivour).

Testing

This has not been tested as the branch does not build at the time of submitting this PR. Happy to test if further instructions provided.

Risk

No public API changes, 5 private static methods and callback instances in DP properties introduced. All changes in the PresentationFramework assembly.

The new behaviour will cause the CanExecute method of commands to be called more often (with every parameter change), and specifically twice during loading of the element (which could be avoided by deferring CanExecute to EndInit phase).

If user changes both parameter and command and changes the command parameter first, with the new behaviour the existing command will potentially be called with a command parameter of an unexpected type. Since the API accepts object though, the implementations of CanExecute should be able to handle both null and any object type.

[ryalanms]

@miloush: As soon as Sam has bandwidth, he will review this. Thanks.

[lindexi]

A year has passed..