整理：C#常用字符串操作，常用数值类型转换

一、字符串操作

1. 字符串连接

//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"

2. 提取字符串中的字符

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

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

3. 字符串大小写转换

string str = "Abc";

//大写
str.ToUpper();    //ABC

//小写
str.ToLower    //abc

4. 拆分字符串为字符串数组

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

5. 字符替换

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

6. 去除字符串首尾空格

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

7. 匹配索引

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

8. 字符串填充，补齐

string str = "";
//左填充
str.PadLeft(,'');    //返回"000666"

//右填充
str.PadRight(,'');    //返回"666000"

9. 字符串格式化（静态方法）

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

10. 判断字符串是否包含指定字符

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

二、常用值类型转换

1. int 类型转换为 string

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

2. string 转换为 int

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

//方法2
result = Convert.ToInt32(a);

//方法3
int.TryParse(a,out result);