You can redefine or overload operators built into C#. Therefore, programmers can also use operators of user-defined types. An overloaded operator is a function with a special name, defined by the keyword operator followed by the symbol of the operator. Like other functions, overloaded operators have a return type and parameter list.
For example, consider the following function:
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;}
The above function implements the addition operator (+) for the user-defined class Box. It adds the properties of two Box objects and returns the added Box object.
Implementation of operator overloading
The following program demonstrates the complete implementation:
using System;namespace OperatorOvlApplication{ class Box { private double length; // 长度 privatedouble breadth; // 宽度 private double height; // 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 + 运算符来把两个 Box 对象相加 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,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 double volume = 0.0; // 体积 // Box1 详述 Box1.setLength(6.0); Box1.setBreadth(7.0); Box1.setHeight(5.0); // Box2 详述 Box2.setLength(12.0); Box2.setBreadth(13.0); Box2.setHeight(10.0); // Box1 的体积 volume = Box1.getVolume(); Console.WriteLine("Box1 的体积: {0}", volume); // Box2 的体积 volume = Box2.getVolume(); Console.WriteLine("Box2 的体积: {0}", volume); // 把两个对象相加 Box3 = Box1 + Box2; // Box3 的体积 volume = Box3.getVolume(); Console.WriteLine("Box3 的体积: {0}", volume); Console.ReadKey(); } } }
When the above code is compiled and executed, it produces the following results:
Box1 的体积: 210 Box2 的体积: 1560 Box3 的体积: 5400
Overloadable and non-overloadable operators
The following table describes the capabilities of operator overloading in C#:
Description | |
These unary operators have only one operand and can be overloaded . | |
These binary operators take two operands and can be overloaded. | |
These comparison operators can be overloaded | |
These conditional logical operators cannot be directly overloaded. | |
These assignment operators cannot be overloaded. | |
These operators cannot be overloaded. |
In view of the above discussion, let us extend the above example and overload more operators:
using System;namespace OperatorOvlApplication{ class Box { private double length; // 长度 privatedouble breadth; // 宽度 private double height; // 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 + 运算符来把两个 Box 对象相加 public static Box operator+ (Box b, Box c) { Box box = newBox(); 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() { returnString.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(); double volume = 0.0; // 体积 // Box1 详述 Box1.setLength(6.0); Box1.setBreadth(7.0); Box1.setHeight(5.0); // Box2 详述 Box2.setLength(12.0); Box2.setBreadth(13.0); Box2.setHeight(10.0); // 使用重载的 ToString() 显示两个盒子 Console.WriteLine("Box1: {0}", Box1.ToString()); Console.WriteLine("Box2: {0}", Box2.ToString()); // Box1 的体积 volume = Box1.getVolume(); Console.WriteLine("Box1 的体积: {0}", volume); // Box2 的体积 volume = Box2.getVolume(); Console.WriteLine("Box2 的体积: {0}", volume); // 把两个对象相加 Box3= Box1 + Box2; Console.WriteLine("Box3: {0}", Box3.ToString()); // Box3 的体积 volume =Box3.getVolume(); Console.WriteLine("Box3 的体积: {0}", volume); //comparing the boxes if (Box1 >Box2) Console.WriteLine("Box1 大于 Box2"); else Console.WriteLine("Box1 不大于 Box2"); if (Box1 <Box2) Console.WriteLine("Box1 小于 Box2"); else Console.WriteLine("Box1 不小于 Box2"); if (Box1>= Box2) Console.WriteLine("Box1 大于等于 Box2"); else Console.WriteLine("Box1 不大于等于 Box2"); if (Box1 <= Box2) Console.WriteLine("Box1 小于等于 Box2"); else Console.WriteLine("Box1 不小于等于 Box2"); if (Box1 != Box2) Console.WriteLine("Box1 不等于 Box2"); else Console.WriteLine("Box1 等于 Box2"); Box4 = Box3; if (Box3 == Box4) Console.WriteLine("Box3 等于 Box4"); else Console.WriteLine("Box3 不等于 Box4"); Console.ReadKey(); } } }
When the above When the code is compiled and executed, it will produce the following results:
Box1: (6, 7, 5) Box2: (12, 13, 10) Box1 的体积: 210 Box2 的体积: 1560 Box3: (18, 20, 15) Box3 的体积: 5400 Box1 不大于 Box2 Box1 小于 Box2 Box1 不大于等于 Box2 Box1 小于等于 Box2 Box1 不等于 Box2 Box3 等于 Box4
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