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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
{
}
}
</div>
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; }
}
</div>
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);
}
</div>
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;
}
</div>
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));
}
}
</div>
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();
}
</div>
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。
</div>