private bool CanAddItemExecute()
        {
            CharacterOnlyRule characterOnlyRule = new CharacterOnlyRule();
            ValidationResult  validationResult  = characterOnlyRule.Validate(NewItem, System.Globalization.CultureInfo.CurrentCulture);

            return(validationResult.IsValid);
        }
        public void ValidateInput_Test()
        {
            //Arrange
            CharacterOnlyRule target = new CharacterOnlyRule();
            object value = "abcd";
            CultureInfo cultureInfo = null;

            //Act
            ValidationResult actual = target.Validate(value, cultureInfo);

            //Assert
            Assert.IsTrue(actual.IsValid);
        }
        private bool CanAddItemExecute()
        {
            CharacterOnlyRule characterOnlyRule = new CharacterOnlyRule();
            ValidationResult validationResult = characterOnlyRule.Validate(NewItem, System.Globalization.CultureInfo.CurrentCulture);

            return validationResult.IsValid;
        }