Creating Validation Engine for Domain Objects

using System;
using System.Collections.Generic;
using System.Text;

namespace ValidationFramework.Library.CustomAttributes
{
    public class RequiredLengthAttribute : ValidationAttribute
    {
        private int _minLength;

        public RequiredLengthAttribute() { }

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

        public override bool IsValid(object item)
        {
            if (((string)item).Length < _minLength)
                return false;

            return true;             
        }
    }
}