# operator (C# Reference)

Use the `operator`

keyword to overload a built-in operator or to provide a user-defined conversion in a class or struct declaration.

## Example

The following is a very simplified class for fractional numbers. It overloads the + and * operators to perform fractional addition and multiplication, and also provides a conversion operator that converts a Fraction type to a double type.

```
class Fraction
{
int num, den;
public Fraction(int num, int den)
{
this.num = num;
this.den = den;
}
// overload operator +
public static Fraction operator +(Fraction a, Fraction b)
{
return new Fraction(a.num * b.den + b.num * a.den,
a.den * b.den);
}
// overload operator *
public static Fraction operator *(Fraction a, Fraction b)
{
return new Fraction(a.num * b.num, a.den * b.den);
}
// user-defined conversion from Fraction to double
public static implicit operator double(Fraction f)
{
return (double)f.num / f.den;
}
}
class Test
{
static void Main()
{
Fraction a = new Fraction(1, 2);
Fraction b = new Fraction(3, 7);
Fraction c = new Fraction(2, 3);
Console.WriteLine((double)(a * b + c));
}
}
/*
Output
0.880952380952381
*/
```

## C# Language Specification

For more information, see the C# Language Specification. The language specification is the definitive source for C# syntax and usage.

## See Also

C# Reference

C# Programming Guide

C# Keywords

implicit

explicit

How to: Implement User-Defined Conversions Between Structs