C#運算子過載

在C#中，可以重新定義或過載大多數內建運算子。 因此，程式員也可以使用具有使用者定義型別的運算子。過載運算子是具有特殊名稱的功能，關鍵字operator後跟定義運算子的符號。 類似於任何其他函式定義，過載運算子具有返回型別和引數列表。

例如，通過以下範例函式：

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;
}

上述函式為使用者自定義Box類實現加法運算子(+)。它實現相加兩個Box物件的屬性，並返回生成的Box物件。

實現操作符過載

以下程式顯示了完整的實現：

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();
        }
    }
}

當編譯和執行上述程式碼時，會產生以下結果：

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

可過載和不可過載的運算子

下表描述了 C# 中過載的運算子：

範例

根據上述討論，我們來擴充套件上面的例子，並且過載更多的運算子：

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();
      }
   }
}

當編譯和執行上述程式碼時，會產生以下結果：

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