public void ChangeInfoContract(BE.Contract c)
//A function that gets Contract after its details have been updated
//The function finds the Contract in the database in the xml file before the update,
//deletes it from the list and adds the Contract after the update
{
XElement root = BasicXML.LoadData();
XElement help;
help = (from item in root.Elements()
where item.Name == "Contract"
where int.Parse(item.Element("NumberOfContract").Value) == c.NumberOfContract
select item).FirstOrDefault();
help.Remove();
root.Add(ExtensionBE.ToXML(c));
BasicXML.Save(root);
}