changes of properties in ExpandableObjectConverter not updating

I'm using ExpandableObjectConverter to group a collection of properties.
it shows fine in the properties window, but the changes doesn't show in the *.Designer.cs file
so every time the desiner is refreshed all my changes gone.

what am I doing wrong?

Code:

---

[TypeConverter(typeof(ExpandableObjectConverter))]
    public class HeaderAppereance
    {
        public HeaderAppereance(Control parent)
        {
            this.Parent = parent;
        }

        private Control Parent;

        private Color backcolor;
        public Color BackColor
        {
            get { return this.backcolor; }
            set { this.backcolor = value; Parent.Refresh(); }
        }

        ....
    }

---

Code:

---

public class MyCustomControl : Panel,StyleNamesFinder
    {
        public MyCustomControl ()
        {

            this.Header = new HeaderAppereance(this);
            ....
        }

          public HeaderAppereance Header { get; set; }

    }

---