C#有关 字符串方法的使用

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication4
{
    class Program
    {
        static void Main(string[] args)
        {
            string Str1 = "download";
            string Str2 = "DOWNLOAD";
            string Str3 = String.Format("{0},{1}!!!",Str1,Str2);
            DateTime dt = DateTime.Now;//获取系统当前日期
            string Str4 = String.Format("{0:D}",dt);
            string Str5 = String.Format("{0:M}", dt);
            string Str6 = "";
            Str6 = Str1.Substring(4,4);//截取字符串
            A Str7 = new A();//实例化类A

            Console.WriteLine(string.Compare(Str1,Str2) );//比较字符串，判断大小，返回0；1；-1
            Console.WriteLine(string.Compare(Str1,Str1));
            Console.WriteLine(string.Compare(Str2,Str1));
            Console.WriteLine(Str1.CompareTo(Str2));
            Console.WriteLine(string.Equals(Str1,Str2));//比较字符串，判断两个字符串是否相等，返回true 或false
            Console.WriteLine(Str1.Equals(Str1));
            Console.WriteLine(Str3);
            Console.WriteLine(Str4);
            Console.WriteLine(dt);
            Console.WriteLine(Str5);
            Console.WriteLine(Str6);
            Str7.my();//调用类A中的方法

            Console .ReadKey();
        }
    }
    class A//声明一个类
    {
        public void my()//声明一个方法
        {
            string StrA = "use^life#download,you";  //声明字符串StrA
            char[] separator= { '^','#',','};  //声明分割字符数组
            String[] splitstrings=new String[100];//声明一个字符串数组
            splitstrings = StrA.Split(separator);//分割字符串
            for (int i = 0; i < splitstrings.Length; i++)//splitstrings.Length等于4
            {
                Console.WriteLine("item{0}:{1}",i,splitstrings[i]);

            }
            Console.ReadKey();
        }
    }
}