Min/Max-value validators in asp.net mvc

问题:

Validation using attributes in asp.net mvc is really nice. I have been using the [Range(min, max)] validator this far for checking values, like e.g.:

[Range(1, 10)]
public int SomeNumber { get; set; }

However - now I need to check the min and max condition separately. I expected to find attributes like these:

[MinValue(1, "Value must be at least 1")]
[MaxValue(10, "Value can't be more than 10")]
public int SomeNumber { get; set; }

Are there any predefined attributes for writing this? Or how do I achieve this?

回答1:

Here is how I would write a validator for MaxValue

public class MaxValueAttribute : ValidationAttribute
    {
        private readonly int _maxValue;

        public MaxValueAttribute(int maxValue)
        {
            _maxValue = maxValue;
        }

        public override bool IsValid(object value)
        {
            return (int) value <= _maxValue;
        }
    }

The MinValue Attribute should be fairly the same

回答2:

I don't think min/max validations attribute exist. I would use something like

[Range(1, Int32.MaxValue)]

for minimum value 1 and

[Range(Int32.MinValue, 10)]

for maximum value 10

回答3:

A complete example of how this could be done. To avoid having to write client-side validation scripts, the existing ValidationType = "range" has been used.

public class MinValueAttribute : ValidationAttribute, IClientValidatable
{
    private readonly double _minValue;

    public MinValueAttribute(double minValue)
    {
        _minValue = minValue;
        ErrorMessage = "Enter a value greater than or equal to " + _minValue;  
    }

    public MinValueAttribute(int minValue)
    {
        _minValue = minValue;
        ErrorMessage = "Enter a value greater than or equal to " + _minValue;
    }

    public override bool IsValid(object value)
    {
        return Convert.ToDouble(value) >= _minValue;
    }

    public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
    {
        var rule = new ModelClientValidationRule();
        rule.ErrorMessage = ErrorMessage;
        rule.ValidationParameters.Add("min", _minValue);
        rule.ValidationParameters.Add("max", Double.MaxValue);
        rule.ValidationType = "range";
        yield return rule;
    }

}

回答4:

jQuery Validation Plugin already implements min and max rules, we just need to create an adapter for our custom attribute:

public class MaxAttribute : ValidationAttribute, IClientValidatable
{
    private readonly int maxValue;

    public MaxAttribute(int maxValue)
    {
        this.maxValue = maxValue;
    }

    public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
    {
        var rule = new ModelClientValidationRule();

        rule.ErrorMessage = ErrorMessageString, maxValue;

        rule.ValidationType = "max";
        rule.ValidationParameters.Add("max", maxValue);
        yield return rule;
    }

    public override bool IsValid(object value)
    {
        return (int)value <= maxValue;
    }
}

Adapter:

$.validator.unobtrusive.adapters.add(
   'max',
   ['max'],
   function (options) {
       options.rules['max'] = parseInt(options.params['max'], 10);
       options.messages['max'] = options.message;
   });

Min attribute would be very similar.