New Post: validate value type short

public class MyClass
{
    public short NumberInput { get; set; }
}

public class MyClassValidator : AbstractValidator<MyClass>
{
    public MyClassValidator()
    {
        RuleFor(x => x.NumberInput)
            .Must(BeNumeric)
            .WithMessage(">> Put your message here to let the user know that their input is not a valid number <<");
    }

    private bool BeNumeric(string input) // Line error (short input)
    {
        int result;
        return int.TryParse(input, out result);
    }
}