C#中this的用法集锦

this 关键字引用类的当前实例，还可用作扩展方法的第一个参数的修饰符。下面就针对this的四种用法，做简单的总结。

首先，我们分别创建user和vip两个c#类

using system;
using system.collections.generic;
using system.linq;
using system.text;
using system.threading.tasks;
 
namespace appconsole
{
 
  /// <summary>
  /// 普通用户
  /// </summary>
  public class user
  {
    /// <summary>
    /// 全局变量
    /// </summary>
    dictionary<string, object> dictinfo = null;
 
    /// <summary>
    /// 构造器
    /// </summary>
    public user()
    {
      dictinfo = new dictionary<string, object>();
    }
 
    /// <summary>
    /// 构造函数重载
    /// </summary>
    /// <param name="userid"></param>
    /// <param name="username"></param>
    public user(int userid, string username)
    {
      this.username = username;
      this.id = userid;
    }
 
    /// <summary>
    /// this，第【1】种用法，索引器
    /// </summary>
    /// <param name="name"></param>
    /// <returns></returns>
    public object this[string name]
    {
      get { return dictinfo[name]; }
      set { dictinfo[name] = value; }
    }
 
 
    /// <summary>
    /// 编号
    /// </summary>
    public int id { get; set; }
 
 
    /// <summary>
    /// 用户名
    /// </summary>
    public string username { get; set; }
 
    /// <summary>
    /// this第【2】种用法，当做参数传递
    /// </summary>
    public void said()
    {
      new vip().say(this);
    }
 
  }
 
  /// <summary>
  /// 会员
  /// </summary>
  public class vip : user
  {
 
 
    /// <summary>
    /// 积分
    /// </summary>
    public int integral { get; set; }
 
    /// <summary>
    /// 构造函数
    /// </summary>
    public vip()
    {
      id = 520;
      integral = 1000;
    }
 
    /// <summary>
    /// this第【3】种用法，通过this()调用无参构造函数
    /// </summary>
    /// <param name="username"></param>
    public vip(string username)
      : this()
    {
      this.username = username;
    }
 
    /// <summary>
    /// 构造函数重载
    /// </summary>
    /// <param name="userid"></param>
    /// <param name="username"></param>
    public vip(int userid, string username)
      : base(userid, username)
    {
 
    }
 
    /// <summary>
    ///say方法
    /// </summary>
    /// <param name="user"></param>
    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));
    }
 
  }
 
  /// <summary>
  /// 静态类，来扩展user类
  /// </summary>
  public static class helper
  {
 
    /// <summary>
    /// 第【4】种用法： this扩展user类
    /// </summary>
    /// <param name="user"></param>
    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));
    }
  }
 
  /// <summary>
  /// 特性类：指定特性仅适用于方法和方法的参数
  /// </summary>
  [system.attributeusage(attributetargets.method | attributetargets.parameter)]
  public class lcqattribute : system.attribute
  {
 
  }
}

this第【1】种用法，索引器

/// <summary>
/// 全局变量
/// </summary>
dictionary<string, object> dictinfo = null;
 
/// <summary>
/// this，第【1】种用法，索引器
/// </summary>
/// <param name="name"></param>
/// <returns></returns>
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

/// <summary>
/// this第【2】种用法，当做参数传递
/// </summary>
public void said()
{
  new vip().say(this);
}

this第【3】种用法，通过this()调用无参构造函数

/// <summary>
/// this第【3】种用法，通过this()调用无参构造函数
/// </summary>
/// <param name="username"></param>
public vip(string username)
  : this()
{
  this.username = username;
}

this第【4】种用法：扩展user类

/// <summary>
/// 静态类，来扩展user类
/// </summary>
public static class helper
{
 
  /// <summary>
  /// 第【4】种用法： this扩展user类
  /// </summary>
  /// <param name="user"></param>
  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));
  }
}

最后，控制台测试

/// <summary>
/// 主程序入口
/// </summary>
/// <param name="args"></param>
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();
 
}

最终结果示意图

以上所述上就是本文的全部内容了，希望大家能够喜欢。