C# - 运算符重载

您可以重新定义或重载 C# 中大多数内置运算符。因此，程序员也可以使用用户定义类型的运算符。重载运算符是具有特殊名称的函数，名称由关键字 operator 加上所定义运算符的符号组成。与其他函数类似，重载运算符具有返回类型和参数列表。

例如，查看以下函数 -

public static Box operator+ (Box b, Box c) {
   Box box = new Box();
   box.length = b.length + c.length;
   box.breadth = b.breadth + c.breadth;
   box.height = b.height + c.height;
   return box;
}

上述函数为用户定义的类 Box 实现了加法运算符 (+)。它将两个 Box 对象的属性相加，并返回结果 Box 对象。

实现运算符重载

以下程序展示了完整的实现 -

using System;

namespace OperatorOvlApplication {
   class Box {
      private double length; // Box 的长度
      private double breadth; // Box 的宽度
      private double height; // Box 的高度

      public double getVolume() {
         return length * breadth * height;
      }
      public void setLength( double len ) {
         length = len;
      }
      public void setBreadth( double bre ) {
         breadth = bre;
      }
      public void setHeight( double hei ) {
         height = hei;
      }
      
      // 重载 + 运算符以添加两个 Box 对象。
      public static Box operator+ (Box b, Box c) {
         Box box = new Box();
         box.length = b.length + c.length;
         box.breadth = b.breadth + c.breadth;
         box.height = b.height + c.height;
         return box;
      }
   }
   class Tester {
      static void Main(string[] args) {
        Box Box1 = new Box(); // 声明 Box1 为 Box 类型
        Box Box2 = new Box(); // 声明 Box2 为 Box 类型
        Box Box3 = new Box(); // 声明 Box3 为 Box 类型
        doublevolume = 0.0; // 在此处存储盒子的体积
        
        // Box1 的规格
         Box1.setLength(6.0);
         Box1.setBreadth(7.0);
         Box1.setHeight(5.0);

         // box 2 的规格
         Box2.setLength(12.0);
         Box2.setBreadth(13.0);
         Box2.setHeight(10.0);

         // Box1 的体积
         volume = Box1.getVolume();
         Console.WriteLine("Volume of Box1 : {0}", volume);

         // Box2 的体积
         volume = Box2.getVolume();
         Console.WriteLine("Volume of Box2 : {0}", volume);

         // 添加两个对象如下:
         Box3 = Box1 + Box2;

         // Box3 的体积
         volume = Box3.getVolume();
         Console.WriteLine("Volume of Box3 : {0}", volume);
         Console.ReadKey();
      }
   }
}

当编译并执行上述代码时，它会产生以下结果 -

Volume of Box1 : 210
Volume of Box2 : 1560
Volume of Box3 : 5400

可重载和不可重载运算符

下表描述了 C# 中运算符的重载能力 -

示例

基于以上讨论，我们扩展前面的示例，并重载其他几个运算符−

using System;

namespace OperatorOvlApplication {
   class Box {
      private double length; // Box 的长度
      private double breadth; // Box 的宽度
      private double height; // Box 的高度
      
      public double getVolume() {
         return length * breadth * height;
      }
      public void setLength( double len ) {
         length = len;
      }
      public void setBreadth( double bre ) {
         breadth = bre;
      }
      public void setHeight( double hei ) {
         height = hei;
      }
      
      // 重载 + 运算符以添加两个 Box 对象。
      public static Box operator+ (Box b, Box c) {
         Box box = new Box();
         box.length = b.length + c.length;
         box.breadth = b.breadth + c.breadth;
         box.height = b.height + c.height;
         return box;
      }
      public static bool operator == (Box lhs, Box rhs) {
         bool status = false;
         if (lhs.length == rhs.length && lhs.height == rhs.height 
            && lhs.breadth == rhs.breadth) {
            
            status = true;
         }
         return status;
      }
      public static bool operator !=(Box lhs, Box rhs) {
         bool status = false;
         
         if (lhs.length != rhs.length || lhs.height != rhs.height || 
            lhs.breadth != rhs.breadth) {
            
            status = true;
         }
         return status;
      }
      public static bool operator <(Box lhs, Box rhs) {
         bool status = false;
         
         if (lhs.length < rhs.length && lhs.height < rhs.height 
            && lhs.breadth < rhs.breadth) {
            
            status = true;
         }
         return status;
      }
      public static bool operator >(Box lhs, Box rhs) {
         bool status = false;
         
         if (lhs.length > rhs.length && lhs.height > 
            rhs.height && lhs.breadth > rhs.breadth) {
            
            status = true;
         }
         return status;
      }
      public static bool operator <=(Box lhs, Box rhs) {
         bool status = false;
         
         if (lhs.length <= rhs.length && lhs.height 
            <= rhs.height && lhs.breadth <= rhs.breadth) {
            
            status = true;
         }
         return status;
      }
      public static bool operator >=(Box lhs, Box rhs) {
         bool status = false;
         
         if (lhs.length >= rhs.length && lhs.height 
            >= rhs.height && lhs.breadth >= rhs.breadth) {
            
            status = true;
         }
         return status;
      }
      public override string ToString() {
         return String.Format("({0}, {1}, {2})", length, breadth, height);
      }
   }
   class Tester {
      static void Main(string[] args) {
        Box Box1 = new Box(); // 声明 Box1 类型为 Box
        Box Box2 = new Box(); // 声明 Box2 类型为 Box
        Box Box3 = new Box(); // 声明 Box3 类型为 Box
        Box Box4 = new Box();
        doublevolume = 0.0; // 在此处存储盒子的体积
        
        // Box1 的规格
        Box1.setLength(6.0);
        Box1.setBreadth(7.0);
        Box1.setHeight(5.0);
        
        // Box2 的规格
        Box2.setLength(12.0);
        Box2.setBreadth(13.0);
        Box2.setHeight(10.0);
        
        // 使用重载的 ToString() 显示盒子:
        Console.WriteLine("Box 1: {0}", Box1.ToString());
        Console.WriteLine("Box 2: {0}", Box2.ToString());
        
        // Box1 的体积
        volume = Box1.getVolume();
        Console.WriteLine("Volume of Box1: {0}",volume);
        
        // Box2 的体积
        volume = Box2.getVolume();
        Console.WriteLine("Volume of  Box2: {0}",volume);
        
        // 添加两个对象，如下所示:
        Box3 = Box1 + Box2;
        Console.WriteLine("Box3: {0}",Box3.ToString());
        
        // Box3 的体积
        volume = Box3.getVolume();
        Console.WriteLine("Volume of Box3 : {0}",volume);
        
        // 比较盒子

         if (Box1 > Box2)
            Console.WriteLine("Box1 is greater than Box2");
         else
            Console.WriteLine("Box1 is not greater than Box2");
         
         if (Box1 < Box2)
            Console.WriteLine("Box1 is less than Box2");
         else
            Console.WriteLine("Box1 is not less than Box2");
         
         if (Box1 >= Box2)
            Console.WriteLine("Box1 is greater or equal to Box2");
         else
            Console.WriteLine("Box1 is not greater or equal to Box2");
         
         if (Box1 <= Box2)
            Console.WriteLine("Box1 is less or equal to Box2");
         else
            Console.WriteLine("Box1 is not less or equal to Box2");
         
         if (Box1 != Box2)
            Console.WriteLine("Box1 is not equal to Box2");
         else
            Console.WriteLine("Box1 is not greater or equal to Box2");
         Box4 = Box3;
         
         if (Box3 == Box4)
            Console.WriteLine("Box3 is equal to Box4");
         else
            Console.WriteLine("Box3 is not equal to Box4");

         Console.ReadKey();
      }
   }
}

当编译并执行上述代码时，它会产生以下结果 -

Box 1: (6, 7, 5)
Box 2: (12, 13, 10)
Volume of Box1 : 210
Volume of Box2 : 1560
Box 3: (18, 20, 15)
Volume of Box3 : 5400
Box1 is not greater than Box2
Box1 is less than Box2
Box1 is not greater or equal to Box2
Box1 is less or equal to Box2
Box1 is not equal to Box2
Box3 is equal to Box4