?????????????????????С???
?????????????????????????????????????????????????????????????????в???????μ??????
?????????????.Net???￡??????????????????д??????????????????????????????????
????---->???????????????????char???????????顣
????--->????????????????????????????????????????char????
???????null????????????????????????null???
??????????????????
????1??ToCharArray():??????????????????char????????顣
????2??new string(char[] chs):???????char????????鷵????????????
????3??ToUpper():????????????д???.
????4??ToLower():???????????Сд???.
????5??Equals(??stringcomprasion......):???????????????????????????Сд??
????(lessonOne.Equals(lessonTwo??StringComparison.OrdinalIgnoreCase))
????Equal??Tostring????object?μ??鷽????????????д
????6??Split():???????????????????????????顣
????string[] nerstr=str.Split(new char[] { ' '?? '??'?? '-' }?? StringSplitOptions.RemoveEmptyEntries);
????7??Contains():?ж????????????????????????
????8??Replace():??????????滻?????????
????9??StartsWith()???ж????????????????????????
????10??EndsWith():?ж?????????????????????????
????11??Trim():????????????????????????????????????м???????
????12??TrimStart():
????13??TrimEnd():
????14??Substring():??????????????????????????????
????15??IndexOf():????????????????е???γ????λ????????У?????-1??
????16??LastIndexof():????????????????к???γ????λ????????У?????-1??
????17?????????
????--->string.IsNullOrEmpyt()?ж?????????????????????null
????--->string.Join():???????????????????????????棬?????????????????????????????С?
????18??????Equals??????
????????string???????????????????Equals?????????????
????//Equals????????????????????????????????????????Equals??????Equals??????д???????????????????????б??
????????????
????//string str = string.Empty;
????//StringBuilder sb = new StringBuilder();
????////00:00:00.1022297
????//Stopwatch sp = new Stopwatch();
????????鷽?????????????????????????????
????//sp.Start();
????//for (int i = 0; i < 100000; i++)
????//{
????//    //str += i;
????//    sb.Append(i); //???
????//}
????//sp.Stop();
????//Console.WriteLine(sp.Elapsed);
??????????????????ó????????????Elapsed
????//Console.WriteLine(sb.ToString());
????StringBuilder sb = new StringBuilder();