Hi Kim, 

I assume you're using PTB? In that case, adding the following code to your Global.asax will make it possible for you to set DefaultValue="-" as a reference to itself.

protected void Application_Start(Object sender, EventArgs e)
{
    ...
    ...
    DataFactory.Instance.LoadedDefaultPageData += new PageEventHandler(Instance_LoadedDefaultPageData);
}

void Instance_LoadedDefaultPageData(object sender, PageEventArgs e)
{
    if (e.Page is PageTypeBuilder.TypedPageData)
    {
        var query = from props in e.Page.GetType().BaseType.GetProperties()
                    let ptbDefaultValues = props.GetCustomAttributes(typeof(PageTypePropertyAttribute), true).OfType<PageTypePropertyAttribute>().Where(a => a.DefaultValue != null && !string.IsNullOrEmpty(a.DefaultValue as string)).ToList()
                    where e.Page[props.Name] == null //Property has no default value from DataFactory
                    && ptbDefaultValues.Count > 0
                    select new { props.Name, ptbDefaultValues.FirstOrDefault().DefaultValue };

        foreach (var prop in query)
        {
            e.Page.Property[prop.Name].ParseToSelf(prop.DefaultValue.ToString());
        }
    }
}

Hope this helps, let me know if you have any questions on this piece of code!

Karoline