public class MyElement : FrameworkElement
{
    public static readonly DependencyProperty IsTabStopProperty;
    public static readonly DependencyProperty TabIndexProperty;


    static Cell()
    {
        IsTabStopProperty = KeyboardNavigation.IsTabStopProperty.AddOwner(typeof(Cell));
        TabIndexProperty = KeyboardNavigation.TabIndexProperty.AddOwner(typeof(Cell));

    }

    public bool IsTabStop
    {
        get
        {
            return (bool)base.GetValue(IsTabStopProperty);
        }
        set
        {
            base.SetValue(IsTabStopProperty, value);
        }
    }

    public int TabIndex
    {
        get
        {
            return (int)base.GetValue(TabIndexProperty);
        }
        set
        {
            base.SetValue(TabIndexProperty, value);
        }
    }
   
    // .............
}