Interaction with Checkable Controls

Many controls (such as Button) supoort a checked state. So the question is, how do you sync up the checked state of a control when there might be multiple control instances that toggle on the same criteria.

An example is the ToggleBold command. There might be an instance of a ToggleBold button in the ribbon and another in the Quick Access Toolbar. They both need to be synced up so that when the selection in the document is bold, the two controls appear checked.

This is done via a ICheckableCommandParameter. By default, the built-in checkable controls assign a CheckableCommandParameter instance (which implements ICheckableCommandParameter) to their CommandParameter property.

When the CanExecute event of the command is handled in your code, set the Handled property of the parameter to true and set the IsChecked property to the checked state value.

This code shows how to handle a ToggleBold command's CanExecute handler to set the checked state of a ribbon control. Note that in this sample code, the SelectionBold property is assumed to return whether the selection in the document is currently bold.

private void OnToggleBoldCanExecute(object sender, CanExecuteRoutedEventArgs e) {
	ICheckableCommandParameter parameter = e.Parameter as ICheckableCommandParameter;
	if (parameter != null) {
		parameter.Handled = true;
		parameter.IsChecked = this.SelectionBold;
	}
}

Since the ribbon controls require the command's can-execute method logic to fire for updating of the checked state, it may be necessary to raise the command's CanExecuteChanged event following a programmatic change that affects the checked state, especially if the command is not a routed command.