C# 重写IComparer 接口

首先定义比较类 继承自IComparer<Racer>

public class RacerComparer : IComparer<Racer>
    {
        public enum CompareType
        {
            FirstName, LastName, Country, Wins
        }
        private CompareType compareType;
        public RacerComparer(CompareType compareType)
        {
            this.compareType = compareType;
        }
        public int Compare(Racer x, Racer y)
        {
            if (x == null && y == null) return 0;
            if (x == null) return -1;
            if (y == null) return 1;

            int result;
            switch (compareType)
            {
                case CompareType.FirstName:
                    return string.Compare(x.FirstName, y.FirstName);
                case CompareType.LastName:
                    return string.Compare(x.LastName, y.LastName);
                case CompareType.Country:
                    result = string.Compare(x.Country, y.Country);
                    if (result == 0)
                        return string.Compare(x.LastName, y.LastName);
                    else
                        return result;
                case CompareType.Wins:
                    return x.Wins.CompareTo(y.Wins);
                default:
                    throw new ArgumentException("Invalid Compare Type");
            }
        }
    }

class Racer : IComparable<Racer>
    {
        public int Id { get; private set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string Country { get; set; }
        public int Wins { get; set; }
        public override string ToString()
        {
            return String.Format("{0} {1}", FirstName, LastName);
        }
        public Racer(int id, string firstName, string lastName, string country)
            : this(id, firstName, lastName, country, wins: 0)
        {
        }
        public Racer(int id, string firstName, string lastName, string country, int wins)
        {
            this.Id = id;
            this.FirstName = firstName;
            this.LastName = lastName;
            this.Country = country;
            this.Wins = wins;
        }
        public int CompareTo(Racer other)
        {
            if (other == null) return -1;
            int compare = string.Compare(this.LastName, other.LastName);
            if (compare == 0)
                return string.Compare(this.FirstName, other.FirstName);
            return compare;
        }
    }

 调用比较方法

 var graham = new Racer(7, "Graham", "Hill", "UK", 14);
            var emerson = new Racer(13, "Emerson", "Fittipaldi", "Brazil", 14);
            var mario = new Racer(16, "Mario", "Andretti", "USA", 12);

            var racers = new List<Racer>(20) { graham, emerson, mario };
 racers.Sort(new RacerComparer(RacerComparer.CompareType.Country));