/// <summary>
/// return the children that untreated
/// </summary>
/// <returns></returns>
public IEnumerable <Child> UntreatedChilds(Func <Child, bool> predicate = null)
{
IEnumerable <Contract> conts = myIdal.GetAllContracts();
IEnumerable <Child> childs;
childs = myIdal.GetAllChilds(predicate).Where(x => !conts.Any(y => y.ChildId == x.Id)); // the childs with no any contract
return(childs);
}