C#運算符重載

在C#中，可以重新定義或重載大多數(shù)內(nèi)置運算符。 因此，程序員也可以使用具有用戶定義類型的運算符。重載運算符是具有特殊名稱的功能，關(guān)鍵字operator后跟定義運算符的符號。 類似于任何其他函數(shù)定義，重載運算符具有返回類型和參數(shù)列表。

例如，通過以下示例函數(shù)：

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;
}

上述函數(shù)為用戶自定義Box類實現(xiàn)加法運算符(+)。它實現(xiàn)相加兩個Box對象的屬性，并返回生成的Box對象。

實現(xiàn)操作符重載

以下程序顯示了完整的實現(xiàn)：

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(60.0);
            Box1.setBreadth(70.0);
            Box1.setHeight(50.0);

            // box 2 specification
            Box2.setLength(121.0);
            Box2.setBreadth(133.0);
            Box2.setHeight(110.0);

            // 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();
        }
    }
}

當(dāng)編譯和執(zhí)行上述代碼時，會產(chǎn)生以下結(jié)果：

Volume of Box1 : 210000
Volume of Box2 : 1770230
Volume of Box3 : 5878880

可重載和不可重載的運算符

下表描述了 C# 中重載的運算符：

示例

根據(jù)上述討論，我們來擴展上面的例子，并且重載更多的運算符：

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  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();
      }
   }
}

當(dāng)編譯和執(zhí)行上述代碼時，會產(chǎn)生以下結(jié)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