C# Operator Overloading
You can redefine or overload the 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 keyword operator followed 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 above function implements the addition operator (+) for a 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
using System;
namespace OperatorOvlApplication
{
class Box
{
private double length; // Length
private double breadth; // Breadth
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 + 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; // Volume
// Box1 specification
Box1.setLength(6.0);
Box1.setBreadth(7.0);
Box1.setHeight(5.0);
// Box2 specification
Box2.setLength(12.0);
Box2.setBreadth(13.0);
Box2.setHeight(10.0);
// 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;
// Volume of Box3
volume = Box3.getVolume();
Console.WriteLine("Volume of Box3 : {0}", volume);
}
}
}
volume = Box3.getVolume();
Console.WriteLine("Volume of Box3: {0}", volume);
Console.ReadKey();
}
}
}
When the above code is compiled and executed, it produces the following result:
Volume of Box1: 210
Volume of Box2: 1560
Volume of Box3: 5400
Overloadable and Non-Overloadable Operators
The following table describes the overloadability of the operators in C#:
| Operator | Description | ||
|---|---|---|---|
| +, -, !, ~, ++, -- | These unary operators take 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 overloaded directly. | ||
| +=, -=, *=, /=, %= | These assignment operators cannot be overloaded. | ||
| =, ., ?:, ->, new, is, sizeof, typeof | These operators cannot be overloaded. |
Example
For the above discussion, let us extend the example by overloading more operators:
Example
using System;
namespace OperatorOvlApplication
{
class Box
{
private double length; // Length
private double breadth; // Breadth
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 + 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)
{
```csharp
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 specification
Box1.setLength(6.0);
Box1.setBreadth(7.0);
Box1.setHeight(5.0);
// Box2 specification
Box2.setLength(12.0);
Box2.setBreadth(13.0);
Box2.setHeight(10.0);
// Displaying the Boxes using the overloaded ToString()
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);
// Adding two objects together
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 is 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();
}
}
}
When the above code is compiled and executed, it produces the following result:
Box1: (6, 7, 5)
Box2: (12, 13, 10)
Volume of Box1: 210
Volume of Box2: 1560
Box3: (18, 20, 15)
Volume of Box3: 5400
Box1 is not greater than Box2
Box1 is less than Box2
Box1 is not greater than or equal to Box2
Box1 is less than or equal to Box2
Box1 is not equal to Box2
Box3 is equal to Box4