public void DelMother(string id)
{
IEnumerable <BE.Contract> contract = dimp.SearchContract(x => x.MomId == id);
if (contract.Count() != 0)
{
throw new Exception("canot delete this mother you have to remove this contract :" + contract.Last().ContractCode);
}
dimp.DelMother(dimp.SearchMother(x => x.MomId == id).Last());
}