public ExtendedListBuilder <TResult> WithValidation(Func <TResult, bool> fn, string errorMessage)
{
ResultValidators.Add(fn, errorMessage);
return(this);
}
public ListBuilder <TResult> WithValidation(Func <TResult, bool> fn, Func <TResult, string> errorMessageFn)
{
ResultValidators.Add(fn, errorMessageFn);
return(this);
}