C#中this的用法集锦

 using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace AppConsole { /// 
 /// 普通用户 /// 
 public class User { /// 
 /// 全局变量 /// 
 Dictionary dictInfo = null; /// 
 /// 构造器 /// 
 public User() { dictInfo = new Dictionary(); } /// 
 /// 构造函数重载 /// 
 ///  ///  public User(int UserID, string UserName) { this.UserName = UserName; this.ID = UserID; } /// 
 /// this，第【1】种用法，索引器 /// 
 ///  ///  public object this[string name] { get { return dictInfo[name]; } set { dictInfo[name] = value; } } /// 
 /// 编号 /// 
 public int ID { get; set; } /// 
 /// 用户名 /// 
 public string UserName { get; set; } /// 
 /// this第【2】种用法，当做参数传递 /// 
 public void Said() { new VIP().Say(this); } } /// 
 /// 会员 /// 
 public class VIP : User { /// 
 /// 积分 /// 
 public int integral { get; set; } /// 
 /// 构造函数 /// 
 public VIP() { ID = 520; integral = 1000; } /// 
 /// this第【3】种用法，通过this()调用无参构造函数 /// 
 ///  public VIP(string UserName) : this() { this.UserName = UserName; } /// 
 /// 构造函数重载 /// 
 ///  ///  public VIP(int UserID, string UserName) : base(UserID, UserName) { } /// 
 ///Say方法 /// 
 ///  public void Say([LCQAttribute] User user) { Console.WriteLine(string.Format("嗨，大家好！我的编号是{0}，大家可以叫我{1}！", user.ID, user.UserName)); } } /// 
 /// 静态类，来扩展User类 /// 
 public static class Helper { /// 
 /// 第【4】种用法： this扩展User类 /// 
 ///  public static void Sing(this User user) { Console.WriteLine(string.Format("嗨，大家好！我的编号是{0}，大家可以叫我{1}！", user.ID, user.UserName)); } } /// 
 /// 特性类：指定特性仅适用于方法和方法的参数 /// 
 [System.AttributeUsage(AttributeTargets.Method | AttributeTargets.Parameter)] public class LCQAttribute : System.Attribute { } } 

 /// 
 /// 全局变量 /// 
 Dictionary dictInfo = null; /// 
 /// this，第【1】种用法，索引器 /// 
 ///  ///  public object this[string name] { get { return dictInfo[name]; } set { dictInfo[name] = value; } } 

 /// 
 /// this第【2】种用法，当做参数传递 /// 
 public void Said() { new VIP().Say(this); } 

 /// 
 /// this第【3】种用法，通过this()调用无参构造函数 /// 
 ///  public VIP(string UserName) : this() { this.UserName = UserName; } 

 /// 
 /// 静态类，来扩展User类 /// 
 public static class Helper { /// 
 /// 第【4】种用法： this扩展User类 /// 
 ///  public static void Sing(this User user) { Console.WriteLine(string.Format("嗨，大家好！我的编号是{0}，大家可以叫我{1}！", user.ID, user.UserName)); } } 

 /// 
 /// 主程序入口 /// 
 ///  static void Main(string[] args) { //0>声明实体 User user = new User(); user.ID = 1; user.UserName = "lichaoqiang"; //第【一】种用法:this用作索引器 public object this[string name]{……} user["UserID"] = 1; Console.WriteLine("第【一】种用法:this用作索引器"); //第【二】种用法:this用作参数传递 user.Say(this); Console.WriteLine("第【二】种用法:this用作参数传递"); user.Said(); //第【三】种用法:this() public VIP:this(){  } VIP vip = new VIP("yezi"); vip.Said(); Console.WriteLine("第【三】种用法:this()"); //第【四】种用法： this扩展VIP类 public static Sing(this User user){……} Console.WriteLine("第【四】种用法： this扩展VIP类"); user.Sing(); Console.Read(); }