插入字符串
public string Insert(int startIndex,string value)
填充字符串
public string PadLeft(int totalWidth,char paddingChar)向左填充
删除字符串
Public String Remove(int startIndex);
Public String Remove(int startIndex,int count);
复制字符串
1、public static string Copy(string str)
2、public void CopyTo(int sourceIndex,char[]destination,int destination,int destinationIndex,intcount)
替换字符串
public string Replace(char OChar,char NChar)
public string Replace(string OValue,string NValue)