AjaxControlToolkit.FilteredTextBoxExtender.CheckIfValid C# (CSharp) Метод

        protected override bool CheckIfValid(bool throwException)
        {
            if(FilterType == FilterTypes.Custom && (
                 (FilterMode == FilterModes.ValidChars && String.IsNullOrEmpty(ValidChars)) ||
                 (FilterMode == FilterModes.InvalidChars && String.IsNullOrEmpty(InvalidChars)))) {
                if(throwException)
                    throw new InvalidOperationException("If FilterTypes.Custom is specified, please provide a value for ValidChars or InvalidChars");

                return false;
            }
            return base.CheckIfValid(throwException);
        }