using System;namespace e1_4_11{    class Program    {        static void Main(string[] args)        {            //字符串搜索            string s = "ABC科学";            int j = s.IndexOf("科");            Console.WriteLine("{0}", j);            string s1 = "abc";            string s2 = "abc";            string s3 = "相同";            //判断连个字符串是否相同            if (s1 == s2)                Console.WriteLine("{0}", s3);            else            {                s3 = "不相同";                Console.WriteLine("{0}", s3);            }            //判断字符串是否为空            string s4 = "";            string s5 = "不空";            if (s4.Length == 0)            {                s5 = "空";                Console.WriteLine("{0}", s5);            }            string s6 = "取子字符串";            //从索引为2开始取2个字符，sb="字符",s内容不变            string sb = s6.Substring(2, 2); //sb="字符"            char sb1 = s6[0];            Console.WriteLine(sb);            Console.WriteLine(sb1);            //删除字符串            string sb2 = s6.Remove(0, 2); //从索引为0开始删除2个字符，sb="字符串",s6内容不变            Console.WriteLine(sb2);            //插入字符串            string s7 = "计算机科学";            string s8 = s7.Insert(3, "软件");            Console.WriteLine(s8);            //替换字符串            string s9 = s7.Replace("计算机", "软件");            Console.WriteLine(s9);            //将字符串转换为字符数组            char[] s10 = s7.ToCharArray(0, s7.Length);            Console.WriteLine(s10);            //转换为字符串            int i = 9;            string s11 = i.ToString();            Console.WriteLine(s11);            //大小写转换            string st = "AaBbCc";            string s12 = st.ToLower();            string s13 = st.ToUpper();            Console.WriteLine(s12);            Console.WriteLine(s13);            //删除所有空格            string sk = "A   bc";            Console.WriteLine(sk.Trim());        }    }}