WPF user control property appears not empty in Visual Studio XAML Properties toolbar

Question

Hello

I'm creating a WPF custom Button Control inheriting from System.Windows.Controls.Button.

using System.ComponentModel;
using System.Windows.Controls;

namespace BMCustomer
{
    public class MyButton : Button
    {
        [Category("MyCategory")]
        [Description("Description for MyText property")]
        //[DefaultValue(null)]
        [DefaultValue("")]
        public string MyText { get; set; }

        //public string MyText
        //{
        //    get { return (string)GetValue(MyTextProperty); }
        //    set { SetValue(MyTextProperty, value); }
        //}

        //public static readonly System.Windows.DependencyProperty MyTextProperty =
        //        System.Windows.DependencyProperty.Register("MyText", typeof(string), typeof(MyButton),
        //        new System.Windows.FrameworkPropertyMetadata(null));

    }
}

When I use MyButton in an XAML and select the Control, the Properties toolbox displays "MyText" property as "MyText" instead of empty. But ContentStringFormat, that is also a string property of the inherited Button, is displayed as empty. See below the image of Visual Studio.

I tried a lot of combinations for this property to be displayed empty with no success: making a DependecyProperty, using DefaultAttribute ...

How can I make this property to be displayed blank when no used?

Thank you in advance