Range annotation between nothing and 100?

Question

I have a [Range] annotation that looks like this:

[Range(0, 100)]
public int AvailabilityGoal { get; set; }

My webpage looks like this:

Answer 1

I guess you could override the Range object and add this behaviour.

public class OptionalRange : RangeAttribute {
    public override bool IsValid(object value) {
        if (value == null || (int)value == 0) return true;
        return base.IsValid(value);
    }
}

Answer 2

This seems to work as (pretty) well:

[Range(Double.NaN, 20)]
public byte? Amount { get; set; }

The lower limit is not checked upon. Not so handy if you want to check null || >= 0. Off course server-side validation goes hand-in-hand with client-side validation where this (< 0) can be checked upon.

Answer 3

You shouldn't have to change the [Range] attribute, as [Range] and other built-in DataAnnotations validators no-op when given an empty value. Just make the property itself of type int? rather than int. Non-nullable ValueType properties (like int) are always automatically required.