To take the currentparent Web URL you have to use this:
var currentSource= HttpContext public override void ItemAdded(SPItemEventProperties properties)
{
using (SPSite site = new SPSite(properties.CurrentSiteId))
{
using (web = site.RequestOpenWeb(properties.UrlReferrerRelativeWebUrl))
{
var parentURL= web.AbsoluteUriParentWeb.Url.ToString();
}
}
}