MVC unobtrusive range validation of dynamic values

Question

I have a value on my model, that must fall within the range of two other values on my model.

For example:

public class RangeValidationSampleModel
{
          


        

Answer 1

custom validation attributes are indeed a good thought. something like (digging up some snippet o'mine found who knows where a while ago):

public sealed class MustBeGreaterThan : ValidationAttribute
{
    private const string _defaultErrorMessage = "'{0}' must be greater than '{1}'";
    private string _basePropertyName;

    public MustBeGreaterThan(string basePropertyName)
        : base(_defaultErrorMessage)
    {
        _basePropertyName = basePropertyName;
    }

    //Override default FormatErrorMessage Method
    public override string FormatErrorMessage(string name)
    {
        return string.Format(_defaultErrorMessage, name, _basePropertyName);
    }

    //Override IsValid
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        var basePropertyInfo = validationContext.ObjectType.GetProperty(_basePropertyName);
        var lowerBound = (int)basePropertyInfo.GetValue(validationContext.ObjectInstance, null);
        var thisValue = (int)value;

        if (thisValue < lowerBound)
        {
            var message = FormatErrorMessage(validationContext.DisplayName);
            return new ValidationResult(message);
        }

        //value validated
        return null;
    }
}

public sealed class MustBeLowerThan : ValidationAttribute
{
    private const string _defaultErrorMessage = "'{0}' must be lower than '{1}'";
    private string _basePropertyName;

    public MustBeLowerThan(string basePropertyName)
        : base(_defaultErrorMessage)
    {
        _basePropertyName = basePropertyName;
    }

    //Override default FormatErrorMessage Method
    public override string FormatErrorMessage(string name)
    {
        return string.Format(_defaultErrorMessage, name, _basePropertyName);
    }

    //Override IsValid
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        var basePropertyInfo = validationContext.ObjectType.GetProperty(_basePropertyName);
        var upperBound = (int)basePropertyInfo.GetValue(validationContext.ObjectInstance, null);
        var thisValue = (int)value;

        if (thisValue > upperBound)
        {
            var message = FormatErrorMessage(validationContext.DisplayName);
            return new ValidationResult(message);
        }

        //value validated
        return null;
    }
}

then decorate your class

public class RangeValidationSampleModel
{
    [MustBeGreaterThan("MinValue")]
    [MustBeLowerThan("MaxValue")]
    int Value { get; set; }

    int MinValue { get; set; }

    int MaxValue { get; set; }
}

and you should be good to go