C# Operator overloading

You can redefine or overload built-in operators in C#. Therefore, programmers can also use operators with user-defined types. Overloaded operators are functions with special names, defined by the keywordoperatorfollowed by the symbol of the operator. Like other functions, overloaded operators have a return type and a 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 function above implements the addition operator (+) for the user-defined class Box. It adds the properties of two Box objects and returns the resulting Box object.

Implementation of operator overloading

The following program demonstrates the complete implementation:

Example

When the above code is compiled and executed, it produces the following result:

Box1 的体积： 210
Box2 的体积： 1560
Box3 的体积： 5400

Operators that can and cannot be overloaded

The following table describes the capabilities of operator overloading in C#:

Operators	Description
+, -, !, ~, ++, --	These unary operators take a single 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 overloaded directly.
+=, -=, *=, /=, %=	These assignment operators cannot be overloaded.
=, ., ?:, ->, new, is, sizeof, typeof	These operators cannot be overloaded.

Example

Based on the above discussion, let us extend the above example to overload more operators:

Example

using System;

namespace OperatorOvlApplication
{
class Box
{
private double length; // Length
private double breadth; // Width
private double height; // Height

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 the + 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; // volume

// Box1 details
Box1.setLength(6.0);
Box1.setBreadth(7.0);
Box1.setHeight(5.0);

// Box2 details
Box2.setLength(12.0);
Box2.setBreadth(13.0);
Box2.setHeight(10.0);

// Use the overloaded ToString() to display the two boxes
Console.WriteLine("Box1： {0}", Box1.ToString());
Console.WriteLine("Box2： {0}", Box2.ToString());

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

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

// add two objects
Box3 = Box1 + Box2;
Console.WriteLine("Box3： {0}", Box3.ToString());
// Volume of Box3
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 than or equal to Box2");
else
Console.WriteLine(Box1 is not greater than or equal to Box2);
if (Box1 <= Box2)
Console.WriteLine("Box1 is less than or equal to Box2");
else
Console.WriteLine(Box1 is not less than or equal to Box2);
if (Box1 != Box2)
Console.WriteLine("Box1 is not equal to Box2");
else
Console.WriteLine(Box1 equals Box2);
Box4 = Box3;
if (Box3 == Box4)
Console.WriteLine(Box3 equals Box4);
else
Console.WriteLine("Box3 is not equal to Box4");

Console.ReadKey();
}
}
}

When the above code is compiled and executed, it produces the following result:

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

other extensions