1.37. C # operator overload

You can redefine or overload the operators built into C #. Therefore, programmers can also use operators of user-defined types. An overloaded operator is a function with a special name that is passed by a keyword operator followed by the symbol of the operator. Like other functions, overloaded operators have return types and parameter lists.

For example, look at 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 theuser-defined class Box . It puts two Box object and returnsthe added Box object.

1.37.1. 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; // 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; } // Overloading 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; } } class Tester { static void Main(string[] args) { Box Box1 = new Box(); // Declare Box1, type is Box Box Box2 = new Box(); // Declare Box2, type is Box Box Box3 = new Box(); // Declare Box3, type is Box double volume = 0.0; // volume // Box1 explain Box1.setLength(6.0); Box1.setBreadth(7.0); Box1.setHeight(5.0); // Box2 explain Box2.setLength(12.0); Box2.setBreadth(13.0); Box2.setHeight(10.0); // Box1's volume volume = Box1.getVolume(); Console.WriteLine("Box1's volume： {0}", volume); // Box2's volume volume = Box2.getVolume(); Console.WriteLine("Box2's volume： {0}", volume); // Add two objects Box3 = Box1 + Box2; // Box3's volume volume = Box3.getVolume(); Console.WriteLine("Box3's volume： {0}", volume); Console.ReadKey(); } } } 

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

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

1.37.2. Overloaded and non-reloadable operators #

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

Operator	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.
=,.,?:->, new, is, sizeof, typeof	These operators cannot be overloaded.

1.37.3. Example #

In response to the above discussion, let’s 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; } // Overloading 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, type is Box Box Box2 = new Box(); // Declare Box2, type is Box Box Box3 = new Box(); // Declare Box3, type is Box Box Box4 = new Box(); double volume = 0.0; // volume // Box1 explain Box1.setLength(6.0); Box1.setBreadth(7.0); Box1.setHeight(5.0); // Box2 explain Box2.setLength(12.0); Box2.setBreadth(13.0); Box2.setHeight(10.0); // Using overloaded ToString() to display two boxes Console.WriteLine("Box1： {0}", Box1.ToString()); Console.WriteLine("Box2： {0}", Box2.ToString()); // Box1's volume volume = Box1.getVolume(); Console.WriteLine("Box1's volume： {0}", volume); // Box2's volume volume = Box2.getVolume(); Console.WriteLine("Box2's volume： {0}", volume); // Add two objects Box3 = Box1 + Box2; Console.WriteLine("Box3： {0}", Box3.ToString()); // Box3's volume volume = Box3.getVolume(); Console.WriteLine("Box3's volume： {0}", volume); //comparing the boxes if (Box1 > Box2) Console.WriteLine("Box1 is greater than Box2"); else Console.WriteLine("Box1 is not more 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 Box2"); else Console.WriteLine("Box1 is not greater than or equal to Box2"); if (Box1 <= Box2) Console.WriteLine("Box1 is less than or equal 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 results:

Box1： (6, 7, 5) Box2： (12, 13, 10) Box1's volume： 210 Box2's volume： 1560 Box3： (18, 20, 15) Box3's volume： 5400 Box1 is not more than Box2 Box1 is less than Box2 Box1 is not greater than or equal to Box2 Box1 is less than or equal Box2 Box1 is not equal to Box2 Box3 is equal to Box4 