OnPropertyChanged with multiple lambdas

class MyClass : INotifyPropertyChanged
{
    private string _foo;
    public string Foo
    {
        get { return _foo; }
        set
        {
            _foo = value;
            OnPropertyChanged(() => Foo, () => Baz);
        }
    }

    private int _bar;
    public int Bar
    {
        get { return _bar; }
        set
        {
            _bar = value;
            OnPropertyChanged(() => Bar, () => Baz);
        }
    }

    public string Baz
    {
        get { return _foo + _bar; }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        var handler = PropertyChanged;
        if (handler != null)
            handler(this, new PropertyChangedEventArgs(propertyName));
    }

    protected void OnPropertyChanged(params Expression<Func<object>>[] propertySelectors)
    {
        foreach (var expr in propertySelectors)
        {
            OnPropertyChanged(ExtractPropertyName(expr));
        }
    }

    protected static string ExtractPropertyName(Expression<Func<object>> propertySelector)
    {
        var memberExpr = propertySelector.Body as MemberExpression;
        if (memberExpr == null)
        {
            // Handle boxing of value types
            var boxingExpr = propertySelector.Body as UnaryExpression;
            if (boxingExpr != null && boxingExpr.NodeType == ExpressionType.Convert && boxingExpr.Type == typeof(object))
            {
                memberExpr = boxingExpr.Operand as MemberExpression;
            }
        }
        if (memberExpr != null)
            return memberExpr.Member.Name;
        throw new ArgumentException("Only member access expressions are supported");
    }
}