Ms Entity Framework Delete Child Object

i have 2 tables without any cascade deletind. i wont to delete parent object with all child objects. i do like this

//get parent object
return _dataContext.Menu.Include("ChildMenu").Include("ParentMenu").Include("Pictures").FirstOrDefault(m => m.MenuId == id);
//then i loop all child objects
var picList = (List<Picture>)menu.Pictures.ToList();
//foreach (var item in menu.Pictures)
for (int i = 0; i < picList.Count; i++)
{
if (File.Exists(HttpContext.Current.Server.MapPath(picList[i].ImgPath)))
{
File.Delete(HttpContext.Current.Server.MapPath(picList[i].ImgPath));
}
if (File.Exists(HttpContext.Current.Server.MapPath(picList[i].ThumbPath)))
{
File.Delete(HttpContext.Current.Server.MapPath(picList[i].ThumbPath));
}
//**what must i do here?**
//menu.Pictures.Remove(picList[i]);
// DataManager dm = new DataManager();
// dm.Picture.Delete(picList[i].Id);
//menu.Pictures.de
//_dataContext.SaveChanges();
//picList[i] = null;
}
//delete parent object
_dataContext.DeleteObject(_dataContext.Menu.Include("ChildMenu").Include("ParentMenu").Include("Pictures").FirstOrDefault(m => m.MenuId == id););
_dataContext.SaveChanges();