Operators

An operator is a member that defines the meaning of an expression operator that can be applied to instances of the class. There are three kinds of operators that can be defined: unary operators, binary operators, and conversion operators.
The following example defines a Digit type that represents decimal digits-integral values between 0 and 9. using System; public struct Digit { byte value; public Digit(byte value) { if (value < 0 || value > 9) throw new ArgumentException(); this.value = value; } public Digit(int value): this((byte) value) {} public static implicit operator byte(Digit d) { return d.value; } public static explicit operator Digit(byte b) { return new Digit(b); } public static Digit operator+(Digit a, Digit b) { return new Digit(a.value + b.value); } public static Digit operator-(Digit a, Digit b) { return new Digit(a.value - b.value); } public static bool operator==(Digit a, Digit b) { return a.value == b.value; } public static bool operator!=(Digit a, Digit b) { return a.value != b.value; } public override bool Equals(object value) { if (value == null) return false; if (GetType() == value.GetType()) return this == (Digit)value; return false; } public override int GetHashCode() { return value.GetHashCode(); } public override string ToString() { return value.ToString(); } } class Test { static void Main() { Digit a = (Digit) 5; Digit b = (Digit) 3; Digit plus = a + b; Digit minus = a - b; bool equals = (a == b); Console.WriteLine("{0} + {1} = {2}", a, b, plus); Console.WriteLine("{0} - {1} = {2}", a, b, minus); Console.WriteLine("{0} == {1} = {2}", a, b, equals); } }
The Digit type defines the following operators: An implicit conversion operator from Digit to byte. An explicit conversion operator from byte to Digit. An addition operator that adds two Digit values and returns a Digit value. A subtraction operator that subtracts one Digit value from another, and returns a Digit value. The equality (==) and inequality (!=) operators, which compare two Digit values.