C# -- 运算符

基本: .  ()  []  x++  x--  new  typeof  checked  unchecked  ->  ::
一元: +  -  !  ~  ++x  --x  (T)x  True  False  &  sizeof
乘除: *  /  %
加减: +  -
移位: <<  >>
关系: <  >  <=  >=  is  as
相等: ==  !=
逻辑: &  ^  |
条件: &&  ||
赋值: =  +=  -=  *=  /=  %=  &=  |=  ^=  <<=  >>=
选择: ?:  ??
其他: =>

整数 / 整数 = 整数

---

using System;
class MyClass
{
static void Main()
{
double d;
d = 14 / 4;
Console.WriteLine(d);    //3
        d = 14 / 4.0;
Console.WriteLine(d);    //3.5
        d = 14.0 / 4.0;
Console.WriteLine(d);    //3.5
        d = 14.0 / 4;
Console.WriteLine(d);    //3.5

Console.WriteLine();
float f;
f = 14 / 4;
Console.WriteLine(f);    //3
        f = (float)(14.0 / 4.0); /* 默认返回 double, 因而需要转换 */
Console.WriteLine(f);    //3.5

Console.WriteLine();
int i;
i = 14 / 4;
Console.WriteLine(i);    //3
        i = (int)(14.0 / 4.0);
Console.WriteLine(i);    //3
        i = 14 % 4;
Console.WriteLine(i);    //2

Console.ReadKey();
}
}

++ -- 可以对 double 类型

---

using System;
class MyClass
{
static void Main()
{
double f = 1.5;
f++; Console.WriteLine(f); //2.5
        f--; Console.WriteLine(f); //1.5
        Console.WriteLine(++f);    //2.5
        Console.WriteLine(--f);    //1.5

Console.ReadKey();
}
}

?:

---

using System;
class MyClass
{
static void Main()
{
int n, a=11, b=22;
n = a > b ? a : b;
Console.WriteLine(n); //22
        n = a < b ? a : b;
Console.WriteLine(n); //11

Console.ReadKey();
}
}

??--左右各两个操作数，左边操作数为null则值右边操作数。?--给变量赋值null

---

using System;
class MyClass
{
static void Main()
{
int? x = null;        /* 给变量赋 null 的写法, 一般用于数值和布尔类型 */
int y;
y = x ?? -1;          /* 如果 x 为 null 将返回后者, 反之返回 x */
Console.WriteLine(y); // -1

x = 9;
y = x ?? -1;
Console.WriteLine(y); // 9

Console.ReadKey();
}
}

=>

---

using System;
using System.Linq;
class MyClass
{
static void Main()
{
int n1, n2;
int[] ns = {22, 333, 4444, 9};
n1 = ns.Max(num => num);
n2 = ns.Min(num => num);
Console.WriteLine("{0}, {1}", n1, n2);       //4444, 9

string[] ss = {"aaa", "bbbb", "ccccc", "dd"};
n1 = ss.Max(str => str.Length);
n2 = ss.Min(str => str.Length);
Console.WriteLine("{0}, {1}", n1, n2);       //5, 2

Console.ReadKey();
}
}

& | ^ !

---

using System;
class MyClass
{
static void Main()
{
bool b;
b = true & true;   Console.WriteLine(b);  // True
        b = true & false;  Console.WriteLine(b);  // False
        b = false & false; Console.WriteLine(b);  // False

b = true | true;   Console.WriteLine(b);  // True
        b = true | false;  Console.WriteLine(b);  // True
        b = false | false; Console.WriteLine(b);  // False

b = true ^ true;   Console.WriteLine(b);  // False
        b = true ^ false;  Console.WriteLine(b);  // True
        b = false ^ false; Console.WriteLine(b);  // False

b = !true;         Console.WriteLine(b);  // False
        b = !false;        Console.WriteLine(b);  // True

Console.ReadKey();
}
}

&& ||; 在条件判断时, 应尽量使用 &&、|| 而不是 &、|; 因为后者总是要计算出结果, 因而会慢(条件运算符专门用于条件判断，只有两个).

---

using System;
class MyClass
{
static void Main()
{
bool b;
/* 在前两种情形下, && 不再判断其后的值 */
b = false && true;  Console.WriteLine(b);  // False
        b = false && false; Console.WriteLine(b);  // False
        b = true && true;   Console.WriteLine(b);  // True
        b = true && false;  Console.WriteLine(b);  // False

/* 在前两种情形下, || 不再判断其后的值 */
b = true || true;   Console.WriteLine(b);  // True
        b = true || false;  Console.WriteLine(b);  // True
        b = false || true;  Console.WriteLine(b);  // True
        b = false || false; Console.WriteLine(b);  // False

Console.ReadKey();
}
}