字符串常用操作

1.比较字符串：Compare、CompareTo、Equals、==、！=
2.定位字符和子串：StartWith/EndsWith、IndexOf/LastIndexOf、IndexOfAny/LastIndexOfAny
3.格式化字符串：Format
4.连接字符串：Concat、Join、+
5.分裂字符串：Split
6.插入和填充字符串：Insert、PadLeft/PagRight
7.删除和剪切字符串：Remove、Trim/TrimStart/TrimEnd
8.复制字符串：Copy、CopyTo
9.替换字符串：Replace
10.更改大小写：ToUpper/ToLower

        Console.WriteLine("-------------------test Join ");
            String str = "";
            String[] strArr = { "aaa", "bbb", "ccc" };
            str = String.Join("+", strArr);
            Console.WriteLine(str); //str="aaa+bbb+ccc"

            Console.WriteLine("-------------------test Format");
            String strA = "Hello";
            String strB = "World";
            str = String.Format("{0},{1}!", strA, strB);
            Console.WriteLine(str);

            Console.WriteLine("-------------------test CompareTo");
            Console.WriteLine(strA.CompareTo(strB));//-1
        Console.WriteLine("abc".CompareTo("abc"));//0
        Console.WriteLine("abc".CompareTo("abcded"));//-1
        Console.WriteLine("abcde".CompareTo("abc"));//1
         Console.WriteLine(string.Compare("abc", "abc")); //0
        Console.WriteLine(string.Compare("abdddc", "abc"));//1 
        Console.WriteLine(string.Compare("abd", "abcdd")); //-1
            Console.WriteLine("-------------------test IndexOf");
            Console.WriteLine(str.IndexOf('l'));
        char [] aaa={'e','H','o'};
            Console.WriteLine(str.IndexOfAny(aaa));  //aaa里的任意字符与str中第一个匹配项的索引,结果为0
        Console.WriteLine(str.LastIndexOfAny(aaa)); //aaa里的任意字符与str中最后一个匹配项的索引,结果为1
            Console.WriteLine("-------------------test Split");
            strArr = str.Split(','); //分裂字符串 结果为：strArr[0]=hello  strArr[1]=world
            int i = 0;
            while (i < strArr.Length)
            {
                Console.WriteLine(strArr[i]);
                i++;
            }

            Console.WriteLine("-------------------test PadLeft");
            str = "hello";
            str = str.PadLeft(20, '*'); //20为填充后的字符串总长度
        str = str.PadLeft(20, '*');
            Console.WriteLine(str);

            Console.WriteLine("-------------------test Remove");
            str = "abcdefg";
            str = str.Remove(1, 3);
            Console.WriteLine(str);

            Console.WriteLine("-------------------test Trim");
            str = "%hello&$#";
            char[] trmchar ={ '%', '&', '$', '#' };
            str = str.Trim(trmchar);
        str = str.TrimStart(trmchar); //只删除开始的trmchar 值，结果为hello&$#
        str = str.TrimEnd(trmchar); //只删除末尾的trmchar 值，结果为%hello
            string str1=string.Copy(str);
            Console.WriteLine(str);