運(yùn)算符重載

你可以重新定義或重載大部分 C# 可用的內(nèi)置操作符。因此，程序員也可以使用用戶定義類型的操作符。重載操作符是特殊關(guān)鍵字 operator 其后跟被定義的名字的符號。像其他函數(shù)一樣，重載操作符也有返回類型和參數(shù)列表。

例如，瀏覽如下函數(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)實(shí)現(xiàn)了用戶定義的 Box 類中加運(yùn)算符，它增加了兩個(gè) Box 對象，并返回這個(gè)結(jié)果 Box 對象。

實(shí)現(xiàn)運(yùn)算符重載

下列程序顯示了完整地實(shí)現(xiàn)：

using System;
namespace OperatorOvlApplication
{
   class Box
   {
      private double length;   // box 的長度
      private double breadth;  // box 的寬度
      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;
      }

      // 重載 + operator 來增加兩個(gè) Box 對象
      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();    // 聲明 box1 為 box 類型
         Box Box2 = new Box();    // 聲明 box2 為 box 類型
         Box Box3 = new Box();   // 聲明 box3 為 box 類型
         double volume = 0.0;    // 在這里存放 box 的體積

         // box 1 詳細(xì)數(shù)據(jù)
         Box1.setLength(6.0);
         Box1.setBreadth(7.0);
         Box1.setHeight(5.0);

         // box 2 詳細(xì)數(shù)據(jù)
         Box2.setLength(12.0);
         Box2.setBreadth(13.0);
         Box2.setHeight(10.0);

         // box 1 的體積
         volume = Box1.getVolume();
         Console.WriteLine("Volume of Box1 : {0}", volume);

         //  box 2 的體積
         volume = Box2.getVolume();
         Console.WriteLine("Volume of Box2 : {0}", volume);

         // 將兩個(gè)對象相加如下：
         Box3 = Box1 + Box2;

         // box 3 的體積
         volume = Box3.getVolume();
         Console.WriteLine("Volume of Box3 : {0}", volume);
         Console.ReadKey();
      }
   }
}

編譯執(zhí)行上述代碼，得到如下結(jié)果：

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

可重載與不可重載的運(yùn)算符

下表列出了 C# 中運(yùn)算符的可重載能力：

示例

針對上述討論，讓我們擴(kuò)展上面的例子，重載更多的操作符：

using System;
namespace OperatorOvlApplication
{
   class Box
   {
      private double length;   // box 的長度
      private double breadth;  // box 的寬度
      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;
      }

      // 重載 + operator 來增加兩個(gè) Box 對象
      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 override string ToString()
      {
         return String.Format("({0}, {1}, {2})", length, breadth, height);
      }
   }

   class Tester
   {
      static void Main(string[] args)
      {
         Box Box1 = new Box();    // 聲明 box1 為 box 類型
         Box Box2 = new Box();    // 聲明 box2 為 box 類型
         Box Box3 = new Box();    // 聲明 box3 為 box 類型
         Box Box4 = new Box();    // 聲明 box4 為 box 類型
         double volume = 0.0;    // 這里存放 box 的體積

         // box 1 詳細(xì)數(shù)據(jù)
         Box1.setLength(6.0);
         Box1.setBreadth(7.0);
         Box1.setHeight(5.0);

         // box 2 詳細(xì)數(shù)據(jù)
         Box2.setLength(12.0);
         Box2.setBreadth(13.0);
         Box2.setHeight(10.0);

         //使用重載的 ToString() 顯示 Boxes 
         Console.WriteLine("Box 1: {0}", Box1.ToString());
         Console.WriteLine("Box 2: {0}", Box2.ToString());

         // box 1 的體積
         volume = Box1.getVolume();
         Console.WriteLine("Volume of Box1 : {0}", volume);

         // box 2 的體積
         volume = Box2.getVolume();
         Console.WriteLine("Volume of Box2 : {0}", volume);

         // 將兩個(gè)對象相加如下：
         Box3 = Box1 + Box2;
         Console.WriteLine("Box 3: {0}", Box3.ToString());

         // box 3 的體積
         volume = Box3.getVolume();
         Console.WriteLine("Volume of Box3 : {0}", volume);

         //比較 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 greater or equal to Box2");
         else
            Console.WriteLine("Box1 is not greater or equal to Box2");

         if (Box1 

編譯執(zhí)行上述代碼，得到如下結(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