Question

I see with the Castle validators I can use a length validation attribute.

    [ValidateLength(6, 30, "some error message")]
    public string SomeProperty { get; set; }

I am trying to find a MinLength only attribute is there a way to do this with the out of the box attributes?

So far my idea is implementing AbstractValidationAttribute

public class ValidateMinLengthAttribute : AbstractValidationAttribute

and making its Build method return a MinLengthValidator, then using ValidateMinLength on SomeProperty

public class MinLengthValidator : Castle.Components.Validator.IValidator

Does anyone have an example of a fully implemented IValidator or know where such documentation exists?? I am not sure what all the methods and properties are expecting.

Thanks

Answer 1

In case anyone else needs help with this I will post the implementation I came up with:

[AttributeUsage(AttributeTargets.Property | AttributeTargets.ReturnValue | AttributeTargets.Parameter, AllowMultiple = true)]
public class ValidateMinLengthAttribute : AbstractValidationAttribute
{
    private IValidator validator;

    public ValidateMinLengthAttribute(int minLength)
    {
        validator = new MinLengthValidator(minLength);
    }

    public ValidateMinLengthAttribute(int minLength, string errorMessage) : base(errorMessage)
    {
        validator = new MinLengthValidator(minLength);
    }

    public override IValidator Build()
    {
        ConfigureValidatorMessage(validator);

        return validator;
    }
}

[Serializable()]
public class MinLengthValidator : AbstractValidator
{
    private int _minLength;
    private const string defaultErrorMessage = "Field must contain at least {0} characters";

    public MinLengthValidator(int minLength)
    {
        _minLength = minLength;
    }

    public override bool IsValid(object instance, object fieldValue)
    {
        if (fieldValue == null) return true;

        return fieldValue.ToString().Length >= _minLength;
    }

    public override bool SupportsBrowserValidation
    {
        get { return true; }
    }

    public override void ApplyBrowserValidation(BrowserValidationConfiguration config, InputElementType inputType, IBrowserValidationGenerator generator, System.Collections.IDictionary attributes, string target)
    {
        base.ApplyBrowserValidation(config, inputType, generator, attributes, target);

        string message = string.Format(defaultErrorMessage, _minLength);
        generator.SetMinLength(target, _minLength, ErrorMessage ?? message);
    }

    protected override string BuildErrorMessage()
    {
        return string.Format(defaultErrorMessage, _minLength);
    }
}