C# IFormattable 接口重写

  public class Racer : IComparable<Racer>, IFormattable
   {
     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 Racer(int id, string firstName, string lastName, string country = null, int wins = )
     {
       this.Id = id;
       this.FirstName = firstName;
       this.LastName = lastName;
       this.Country = country;
       this.Wins = wins;
     }

     public override string ToString()
     {
       return String.Format("{0} {1}", FirstName, LastName);
     }

     public string ToString(string format, IFormatProvider formatProvider)
     {
       if (format == null) format = "N";
       switch (format.ToUpper())
       {
         case "N": // name
           return ToString();
         case "F": // first name
           return FirstName;
         case "L": // last name
           return LastName;
         case "W": // Wins
           return String.Format("{0}, Wins: {1}", ToString(), Wins);
         case "C": // Country
           return String.Format("{0}, Country: {1}", ToString(), Country);
         case "A": // All
           return String.Format("{0}, {1} Wins: {2}", ToString(), Country, Wins);
         default:
           throw new FormatException(String.Format(formatProvider,
                 "Format {0} is not supported", format));
       }
     }

     public string ToString(string format)
     {
       return ToString(format, null);
     }

     public int CompareTo(Racer other)
     {
       int compare = this.LastName.CompareTo(other.LastName);
       if (compare == )
         return this.FirstName.CompareTo(other.FirstName);
       return compare;
     }
   }