//将指定的数组所有元素拼接为一个字符串
string[] arr = {"A","B","C"};
string.Concat(arr);

//使用连字符将数组拼接为字符串
string.Join(",",arr);    //输出"A,B,C"

//获取字符串中的某个char 字符
string str = "Hello";
char ch = str[4];    //ch = ‘o‘

//字符串截取 顾头不顾尾 从0开始
string newStr = str.Substring(0,1);    //newStr = "H"

string str = "Abc";

//大写
str.ToUpper();    //ABC

//小写
str.ToLower    //abc

string str = "A,B,C";
string[] arr = str.Split(‘,‘);    //arr {"A","B","C"}

//将str的"_"替换为","
string str = "A_B_C";
str.Replace(‘_‘,",");    //str = "A,B,C"

string str = "A B C";
string newStr = str.Trim();    //newStr = "ABC"

string str = "ABCDE";
int index = str.IndexOf(‘A‘);    //index = 0

string str = "666";
//左填充
str.PadLeft(6,‘0‘);    //返回"000666"

//右填充
str.PadRight(6,‘0‘);    //返回"666000"

string str = string.Format("{0}---{1}",pig,dog);    //str = "pig---dog"

string a = "I am Mike";
string b = "Mike";
bool result = a.Contains(b);    //result = true

int a = 250;
string b = a.ToString();    //b = "250"

string a = "250";
int result;
//方法1
result = int.Parse(a);

//方法2
result = Convert.ToInt32(a);

//方法3
int.TryParse(a,out result);