C# 文法練習(3): 運算子

基本: .  ()  []  x++  x--  new  typeof  checked  unchecked  ->  ::一元: +  -  !  ~  ++x  --x  (T)x  True  False  &  sizeof乘除: *  /  %加減: +  -移位: >關係:   =  is  as  相等: ==  !=邏輯: &  ^  |條件: &&  ||賦值: =  +=  -=  *=  /=  %=  &=  |=  ^=  >=  選擇: ?:  ??其他: =>

整數 / 整數 = 整數

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); /* 預設返回 double, 因而需要轉換 */        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();    }}

++ -- 可以對 double 類型

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 

??

using System;class MyClass{    static void Main()    {        int? x = null;        /* 給變數賦 null 的寫法, 一般用於數值和布爾類型 */        int y;        y = x ?? -1;          /* 如果 x 為 null 將返回後者, 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();    }}

&& ||; 在條件判斷時, 應盡量使用 &&、|| 而不是 &、|; 因為後者總是要計算出結果, 因而會慢.

using System;class MyClass{    static void Main()    {        bool b;        /* 在前兩種情形下, && 不再判斷其後的值 */        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        /* 在前兩種情形下, || 不再判斷其後的值 */        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();    }}