namespace ABC
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Contact> list = new List<Contact>() { new Contact(){FirstName="A",LastName="B"},
            new Contact(){FirstName="A",LastName="A"},new Contact(){FirstName="A",LastName="C"},
            };
           //Compare(Contact x, Contact y)怎么把写好的方法带入下面的红色函数
            list = list.Sort(“函数”);
           
        }
    }
    class Contact
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }
    class NameCompare : IComparer<Contact>
    {
        public int Compare(Contact x, Contact y)
        {
            int result;
            if (Contact.ReferenceEquals(x, y))
            {
                result = 0;
            }
            else
            {
                if(x==null)
                {
                    result=1;
                }
                else if (y == null)
                {
                    result = -1;
                }
                else
                {
                    result = StringCompare(x.LastName, y.LastName);
                        if(result==0)
                        {
                            result=StringCompare(x.FirstName,y.FirstName);
                        }
                }
            }
            return result;
        }
        private static int StringCompare(string x, string y)
        {
            int result;
            if (x == null)
            {
                if (y == null)
                {
                    result = 0;
                }
                else
                {
                    result = 1;
                }
            }
            else
            {
                result = x.CompareTo(y);
            }
            return result;
        }
    }
}