当我们需要使用多个构造器的时候，为了减少代码量，可以使用this来调用自身的构造器

1 using System; 2 using System.Collections.Generic; 3 using System.Linq; 4 using System.Text; 5 using System.Threading.Tasks; 6  7 namespace ALTest.Employee 8 { 9     class Employee210     {11 12         public Employee2(string firstName, string lastName)13         {14             FirstName = firstName;15             LastName = lastName;16         }17 18 19         //  :this (firstName,lastName) 调用了 public Employee2(string firstName, string lastName) 构造器20         public Employee2(21             int id,string firstName, string lastName)22             :this (firstName,lastName)23         {24             Id = id;25         }26 27 28         public int Id { get; set; }29         public string FirstName { get; private set; }30         public string LastName { get; private set; }31         public string  Salary { get; set; }32         public string Title { get; set; }33 34     }35 }