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C#中this的用法集錦

更新時(shí)間：2015年06月04日 09:14:28 投稿：hebedich

本文給大家匯總介紹了C#中的幾種this用法，相信大家應(yīng)該有用過(guò)，但你用過(guò)幾種？以下是個(gè)人總結(jié)的this幾種用法，歡迎大家拍磚，廢話少說(shuō)，直接列出用法及相關(guān)代碼。

this 關(guān)鍵字引用類的當(dāng)前實(shí)例，還可用作擴(kuò)展方法的第一個(gè)參數(shù)的修飾符。下面就針對(duì)this的四種用法，做簡(jiǎn)單的總結(jié)。

首先，我們分別創(chuàng)建User和VIP兩個(gè)C#類

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
 
namespace AppConsole
{
 
  /// <summary>
  /// 普通用戶
  /// </summary>
  public class User
  {
    /// <summary>
    /// 全局變量
    /// </summary>
    Dictionary<string, object> dictInfo = null;
 
    /// <summary>
    /// 構(gòu)造器
    /// </summary>
    public User()
    {
      dictInfo = new Dictionary<string, object>();
    }
 
    /// <summary>
    /// 構(gòu)造函數(shù)重載
    /// </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】種用法，索引器
    /// </summary>
    /// <param name="name"></param>
    /// <returns></returns>
    public object this[string name]
    {
      get { return dictInfo[name]; }
      set { dictInfo[name] = value; }
    }
 
 
    /// <summary>
    /// 編號(hào)
    /// </summary>
    public int ID { get; set; }
 
 
    /// <summary>
    /// 用戶名
    /// </summary>
    public string UserName { get; set; }
 
    /// <summary>
    /// this第【2】種用法，當(dāng)做參數(shù)傳遞
    /// </summary>
    public void Said()
    {
      new VIP().Say(this);
    }
 
  }
 
  /// <summary>
  /// 會(huì)員
  /// </summary>
  public class VIP : User
  {
 
 
    /// <summary>
    /// 積分
    /// </summary>
    public int integral { get; set; }
 
    /// <summary>
    /// 構(gòu)造函數(shù)
    /// </summary>
    public VIP()
    {
      ID = 520;
      integral = 1000;
    }
 
    /// <summary>
    /// this第【3】種用法，通過(guò)this()調(diào)用無(wú)參構(gòu)造函數(shù)
    /// </summary>
    /// <param name="UserName"></param>
    public VIP(string UserName)
      : this()
    {
      this.UserName = UserName;
    }
 
    /// <summary>
    /// 構(gòu)造函數(shù)重載
    /// </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！我的編號(hào)是{0}，大家可以叫我{1}！", user.ID, user.UserName));
    }
 
  }
 
  /// <summary>
  /// 靜態(tài)類，來(lái)擴(kuò)展User類
  /// </summary>
  public static class Helper
  {
 
    /// <summary>
    /// 第【4】種用法： this擴(kuò)展User類
    /// </summary>
    /// <param name="user"></param>
    public static void Sing(this User user)
    {
      Console.WriteLine(string.Format("嗨，大家好！我的編號(hào)是{0}，大家可以叫我{1}！", user.ID, user.UserName));
    }
  }
 
  /// <summary>
  /// 特性類：指定特性僅適用于方法和方法的參數(shù)
  /// </summary>
  [System.AttributeUsage(AttributeTargets.Method | AttributeTargets.Parameter)]
  public class LCQAttribute : System.Attribute
  {
 
  }
}

this第【1】種用法，索引器

/// <summary>
/// 全局變量
/// </summary>
Dictionary<string, object> dictInfo = null;
 
/// <summary>
/// this，第【1】種用法，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】種用法，當(dāng)做參數(shù)傳遞

/// <summary>
/// this第【2】種用法，當(dāng)做參數(shù)傳遞
/// </summary>
public void Said()
{
  new VIP().Say(this);
}

this第【3】種用法，通過(guò)this()調(diào)用無(wú)參構(gòu)造函數(shù)

/// <summary>
/// this第【3】種用法，通過(guò)this()調(diào)用無(wú)參構(gòu)造函數(shù)
/// </summary>
/// <param name="UserName"></param>
public VIP(string UserName)
  : this()
{
  this.UserName = UserName;
}

this第【4】種用法：擴(kuò)展User類

/// <summary>
/// 靜態(tài)類，來(lái)擴(kuò)展User類
/// </summary>
public static class Helper
{
 
  /// <summary>
  /// 第【4】種用法： this擴(kuò)展User類
  /// </summary>
  /// <param name="user"></param>
  public static void Sing(this User user)
  {
    Console.WriteLine(string.Format("嗨，大家好！我的編號(hào)是{0}，大家可以叫我{1}！", user.ID, user.UserName));
  }
}

最后，控制臺(tái)測(cè)試

/// <summary>
/// 主程序入口
/// </summary>
/// <param name="args"></param>
static void Main(string[] args)
{
 
  //0>聲明實(shí)體
  User user = new User();
  user.ID = 1;
  user.UserName = "lichaoqiang";
 
  //第【一】種用法:this用作索引器 public object this[string name]{……}
  user["UserID"] = 1;
  Console.WriteLine("第【一】種用法:this用作索引器");
 
  //第【二】種用法:this用作參數(shù)傳遞 user.Say(this);
  Console.WriteLine("第【二】種用法:this用作參數(shù)傳遞");
  user.Said();
 
  //第【三】種用法:this() public VIP:this(){  }
  VIP vip = new VIP("yezi");
  vip.Said();
  Console.WriteLine("第【三】種用法:this()");
 
  //第【四】種用法： this擴(kuò)展VIP類 public static Sing(this User user){……}
  Console.WriteLine("第【四】種用法： this擴(kuò)展VIP類");
  user.Sing();
 
 
  Console.Read();
 
}

最終結(jié)果示意圖