NerdDinner turorial：以下方法或属性之间的调用不明确

Question

我正在逐步完成ASP.NET NerdDinner教程，并进入此步骤http://www.asp.net/mvc/overview/older-versions-1/nerddinner/build-a-model-with-business-rule-validations。 我完成了与教程完全相同的任务（除了项目名称），我收到以下错误：

The call is ambiguous between the following methods or properties: 'AdventureTrip.Models.Trip.GetRuleViolations()' and 'AdventureTrip.Models.Trip.GetRuleViolations()'

任何想法如何解决这个问题？

Trip.cs：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Text.RegularExpressions;
using System.Data.Linq;

namespace AdventureTrip.Models
{
    public partial class Trip
    {
        public bool IsValid
        {
            get { return (GetRuleViolations().Count() == 0); }
        }

        public IEnumerable<RuleViolation> GetRuleViolations()
        {
            yield break;
        }

        partial void OnValidate(ChangeAction action)
        {
            if (!IsValid)
                throw new ApplicationException("Rule violation prevent saving");
        }
    }

    public partial class Trip
    {
        public IEnumerable<RuleViolation> GetRuleViolations()
        {
            if (String.IsNullOrEmpty(Title))
                yield return new RuleViolation("Title required", "Title");

            if (String.IsNullOrEmpty(Description))
                yield return new RuleViolation("Description required", "Description");

            if (String.IsNullOrEmpty(OrganisedBy))
                yield return new RuleViolation("HostedBy required", "HostedBy");

            if (String.IsNullOrEmpty(Address))
                yield return new RuleViolation("Address required", "Address");

            if (String.IsNullOrEmpty(Country))
                yield return new RuleViolation("Country required", "Country");

            if (String.IsNullOrEmpty(ContactPhone))
                yield return new RuleViolation("Phone# required", "ContactPhone");

            if (!PhoneValidator.IsValidNumber(ContactPhone, Country))
                yield return new RuleViolation("Phone# does not match country", "ContactPhone");
            yield break;
        }
        public class PhoneValidator
        {
            static IDictionary<string, Regex> countryRegex = new Dictionary<string, Regex>() 
            {
                { "USA", new Regex("^[2-9]\\d{2}-\\d{3}-\\d{4}$")},
                { "UK", new Regex("(^1300\\d{6}$)|(^1800|1900|1902\\d{6}$)|(^0[2|3|7|8]{1}[0-9]{8}$)|(^13\\d{4}$)|(^04\\d{2,3}\\d{6}$)")},
                { "Netherlands", new Regex("(^\\+[0-9]{2}|^\\+[0-9]{2}\\(0\\)|^\\(\\+[0-9]{2}\\)\\(0\\)|^00[0-9]{2}|^0)([0-9]{9}$|[0-9\\-\\s]{10}$)")},
            };
            public static bool IsValidNumber(string phoneNumber, string country)
            {
                if (country != null && countryRegex.ContainsKey(country))
                    return countryRegex[country].IsMatch(phoneNumber);
                else
                    return false;
            }
            public static IEnumerable<string> Countries
            {
                get { return countryRegex.Keys; }
            }
        }
    }

    public class RuleViolation
    {
        public string ErrorMessage { get; private set; }
        public string PropertyName { get; private set; }

        public RuleViolation(string errorMessage)
        {
            ErrorMessage = errorMessage;
        }

        public RuleViolation(string errorMessage, string propertyName)
        {
            ErrorMessage = errorMessage;
            PropertyName = propertyName;
        }
    }
}