this 关键字的含义？

Code
using System;
using System.Collections.Generic;
using System.Text;
 
namespace Example10
{
    class Class1
    {
        private double c;
        private string value;
 
        public double C
        {
            get
            {
                return c;
            }
        }
        public Class1(double c)
        {
            //限定同名的隐藏成员
            this.c = c;
        }
        public Class1(Class1 value)
        {
            //用对象本身实例化自己没有意义
            if (this != value)
            {
                c = value.C;
            }
        }
        public override string ToString()
        {
            //将对象本身做为参数
            return string.Format("{0} Celsius = {1} Fahrenheit", c, UnitTransClass.C2F(this));
        }
 
        //由于好奇，在这做了一个效率测试，想看看到底哪种方式访问成员变量更快，结论：区别不大。。。
        public string Test1()
        {
            long vTickCount = Environment.TickCount;
            for (int i = 0; i < 10000000; i++)
                this.value = i.ToString();
            return string.Format("Have this.: {0} MSEL", Environment.TickCount - vTickCount);
        }
        public string Test2()
        {
            long vTickCount = Environment.TickCount;
            for (int i = 0; i < 10000000; i++)
                value = i.ToString();
            return string.Format("Don't have this.: {0} MSEL", Environment.TickCount - vTickCount);
        }
    }
    class UnitTransClass
    {
        public static double C2F(Class1 value)
        {
            //摄氏到华氏的转换公式
            return 1.8 * value.C + 32;
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            Class1 tmpObj = new Class1(37.5);
            Console.WriteLine(tmpObj);
            Console.WriteLine(tmpObj.Test1());
            Console.WriteLine(tmpObj.Test2());
            Console.ReadLine();
        }
    }
}