Operator 重载

您可以重新定义或重载C＃中可用的大多数内置运算符。 因此，程序员也可以使用具有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，关键字operator后跟要定义的运算符的符号。 与任何其他函数类似，重载运算符具有返回类型和参数列表。

例如，通过以下功能 -

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;
}

上面的函数为用户定义的类Box实现了加法运算符（+）。 它添加了两个Box对象的属性并返回结果Box对象。

实现运算符重载

以下程序显示了完整的实现 -

using System;
namespace OperatorOvlApplication {
   class Box {
      private double length;   // Length of a box
      private double breadth;  // Breadth of a box
      private double height;   // Height of a box
      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;
      }
      // Overload + operator to add two Box objects.
      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();   // Declare Box1 of type Box
         Box Box2 = new Box();   // Declare Box2 of type Box
         Box Box3 = new Box();   // Declare Box3 of type Box
         double volume = 0.0;    // Store the volume of a box here
         // box 1 specification
         Box1.setLength(6.0);
         Box1.setBreadth(7.0);
         Box1.setHeight(5.0);
         // box 2 specification
         Box2.setLength(12.0);
         Box2.setBreadth(13.0);
         Box2.setHeight(10.0);
         // volume of box 1
         volume = Box1.getVolume();
         Console.WriteLine("Volume of Box1 : {0}", volume);
         // volume of box 2
         volume = Box2.getVolume();
         Console.WriteLine("Volume of Box2 : {0}", volume);
         // Add two object as follows:
         Box3 = Box1 + Box2;
         // volume of box 3
         volume = Box3.getVolume();
         Console.WriteLine("Volume of Box3 : {0}", volume);
         Console.ReadKey();
      }
   }
}

编译并执行上述代码时，会产生以下结果 -

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

可过载和不可重载的运算符

下表描述了C＃中运算符的重载能力 -

例子 (Example)

根据上述讨论，让我们扩展前面的例子，并重载几个运算符 -

using System;
namespace OperatorOvlApplication {
   class Box {
      private double length;    // Length of a box
      private double breadth;   // Breadth of a box
      private double height;    // Height of a box
      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;
      }
      // Overload + operator to add two Box objects.
      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();   // Declare Box1 of type Box
         Box Box2 = new Box();   // Declare Box2 of type Box
         Box Box3 = new Box();   // Declare Box3 of type Box
         Box Box4 = new Box();
         double volume = 0.0;    // Store the volume of a box here
         // box 1 specification
         Box1.setLength(6.0);
         Box1.setBreadth(7.0);
         Box1.setHeight(5.0);
         // box 2 specification
         Box2.setLength(12.0);
         Box2.setBreadth(13.0);
         Box2.setHeight(10.0);
         //displaying the Boxes using the overloaded ToString():
         Console.WriteLine("Box 1: {0}", Box1.ToString());
         Console.WriteLine("Box 2: {0}", Box2.ToString());
         // volume of box 1
         volume = Box1.getVolume();
         Console.WriteLine("Volume of Box1 : {0}", volume);
         // volume of box 2
         volume = Box2.getVolume();
         Console.WriteLine("Volume of Box2 : {0}", volume);
         // Add two object as follows:
         Box3 = Box1 + Box2;
         Console.WriteLine("Box 3: {0}", Box3.ToString());
         // volume of box 3
         volume = Box3.getVolume();
         Console.WriteLine("Volume of Box3 : {0}", volume);
         //comparing the boxes
         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();
      }
   }
}

编译并执行上述代码时，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