Comparing 2 model properties

Attribute.cs

 [AttributeUsage(AttributeTargets.Class)]
    public class MatchAttribute : ValidationAttribute
    {
        public String SourceProperty { get; set; }
        public String MatchProperty { get; set; }

        public MatchAttribute(string source, string match)
        {
            SourceProperty = source;
            MatchProperty = match;
        }

        public override Boolean IsValid(Object value)
        {
            if (value == null)
                return false;

            Type objectType = value.GetType();

            PropertyInfo[] properties = objectType.GetProperties();

            object sourceValue = new object();
            object matchValue = new object();

            Type sourceType = null;
            Type matchType = null;

            int counter = 0;

            foreach (PropertyInfo propertyInfo in properties)
            {
                if (propertyInfo.Name == SourceProperty || propertyInfo.Name == MatchProperty)
                {
                    if (counter == 0)
                    {
                        sourceValue = propertyInfo.GetValue(value, null);
                        sourceType = propertyInfo.GetValue(value, null).GetType();
                    }
                    if (counter == 1)
                    {
                        matchValue = propertyInfo.GetValue(value, null);
                        matchType = propertyInfo.GetValue(value, null).GetType();
                    }
                    counter++;
                    if (counter == 2)
                    {
                        break;
                    }
                }
            }

            if (sourceType != null && matchType != null)
            {
                //if (Convert.ChangeType(sourceValue, sourceType) == Convert.ChangeType(matchValue, matchType))
                return String.Equals(sourceValue.ToString(), matchValue.ToString());
            }
            return false;
        }
    }

Model.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.ComponentModel.DataAnnotations;
using DinnerParty.Models.CustomAnnotations;

namespace DinnerParty.Models
{
    [Match("Password", "ConfirmPassword", ErrorMessage = "Passwords must match")]
    public class RegisterModel
    {
        [Required]
        public string UserName { get; set; }

        [Required]
        [RegularExpression(@"^((([a-z]|\d|[!#\$%&'\*\+\-\/=\?\^_`{\|}~]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])+(\.([a-z]|\d|[!#\$%&'\*\+\-\/=\?\^_`{\|}~]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])+)*)|((\x22)((((\x20|\x09)*(\x0d\x0a))?(\x20|\x09)+)?(([\x01-\x08\x0b\x0c\x0e-\x1f\x7f]|\x21|[\x23-\x5b]|[\x5d-\x7e]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(\\([\x01-\x09\x0b\x0c\x0d-\x7f]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF]))))*(((\x20|\x09)*(\x0d\x0a))?(\x20|\x09)+)?(\x22)))@((([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])*([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])))\.)+(([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])*([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])))\.?$", ErrorMessage = "Please enter a valid email address")]
        public string Email { get; set; }

        [StringLength(18, MinimumLength = 8, ErrorMessage = "Password lengths must be between 8 and 18 characters in length"), Required]
        public string Password { get; set; }

        [Required]
        public string ConfirmPassword { get; set; }

    }
}