Operator Overloading With C#

Operator overloading allows programmers tobuild types which feel as natural to use as simple types (int, long,etc.). C# implements a stricter version of operator overloading in C++,but it allows classes such as the quintessential example ofoperator-overloading, the complex number class, to work well.

In C#, the == operator is a non-virtual(operators can't be virtual) method of the object class which comparesby reference. When you build a class, you may define your own ==operator. If you are using your class with collections, then you shouldimplement the IComparable interface. This interface has one method toimplement, called the CompareTo (object) method, which should returnpositive, negative, or 0 if \"this\" is greater, less than, or the samevalue as the object. You may choose to define <, <=, >=, >methods if you want users of your class to have a nicer syntax. Thenumeric types (int, long, etc) implement the IComparable interface.

Here's a simple example of how to deal with equality and comparisons:

public class Score : IComparable
{
int value;

public Score (int score) {
value = score;
}

public static bool operator == (Score x, Score y) {
return x.value == y.value;
}

public static bool operator != (Score x, Score y) {
return x.value != y.value;
}

public int CompareTo (object o) {
return value – ((Score)o).value;
}
}

Score a = new Score (5);
Score b = new Score (5);
Object c = a;
Object d = b;

To compare a and b by reference:

System.Console.WriteLine ((object)a == (object)b; // false
To compare a and b by value:

System.Console.WriteLine (a == b); // true
To compare c and d by reference:

System.Console.WriteLine (c == d); // false
To compare c and d by value:

System.Console.WriteLine (((IComparable)c).CompareTo (d) == 0); // trueYou could also add the <, <=, >=, > operators to the score class.
C#ensures at compile time that operators which are logically paired (!=and ==, > and <, >= and <=), must both be defined