WPF - How to force a Command to re-evaluate 'CanExecute' via its CommandBindings

Question

I have a Menu where each MenuItem in the hierarchy has its Command property set to a RoutedCommand I\'ve defined. The as

Answer 1

I couldnt use CommandManager.InvalidateRequerySuggested(); because I was getting performance hit.

I have used MVVM Helper's Delegating command, which looks like below (i have tweaked it a bit for our req). you have to call command.RaiseCanExecuteChanged() from VM

public event EventHandler CanExecuteChanged
{
    add
    {
        _internalCanExecuteChanged += value;
        CommandManager.RequerySuggested += value;
    }
    remove
    {
        _internalCanExecuteChanged -= value;
        CommandManager.RequerySuggested -= value;
    }
}

/// 

/// This method can be used to raise the CanExecuteChanged handler.
/// This will force WPF to re-query the status of this command directly.
/// 
public void RaiseCanExecuteChanged()
{
    if (canExecute != null)
        OnCanExecuteChanged();
}

/// 

/// This method is used to walk the delegate chain and well WPF that
/// our command execution status has changed.
/// 
protected virtual void OnCanExecuteChanged()
{
    EventHandler eCanExecuteChanged = _internalCanExecuteChanged;
    if (eCanExecuteChanged != null)
        eCanExecuteChanged(this, EventArgs.Empty);
}