silverlight为控件注册属性

public class ComboBoxClassic : ComboBox
    {
        #region SelectedValuePathProperty
        public static readonly DependencyProperty SelectedValuePathProperty = 
            DependencyProperty.Register("SelectedValuePath", typeof(string), 
            typeof(ComboBoxClassic), null);
        public string SelectedValuePath
        {
            get
            {
                return (string)GetValue(ComboBoxClassic.SelectedValuePathProperty);
            }
            set
            {
                SetValue(ComboBoxClassic.SelectedValuePathProperty, value);
            }
        }
        #endregion
}