Algorithm
In C#, an interface is a way to define a contract for a class without specifying the implementation details. It allows you to declare a set of methods, properties, events, or indexers that a class must implement. Interfaces provide a mechanism for achieving multiple inheritance in C#.
Code Examples
#1 Implementing an Interface in C#
Code -
C# Programming
using System;
namespace CsharpInterface {
interface IPolygon {
// method without body
void calculateArea(int l, int b);
}
class Rectangle : IPolygon {
// implementation of methods inside interface
public void calculateArea(int l, int b) {
int area = l * b;
Console.WriteLine("Area of Rectangle: " + area);
}
}
class Program {
static void Main (string [] args) {
Rectangle r1 = new Rectangle();
r1.calculateArea(100, 200);
}
}
}Output
Area of Rectangle: 20000
#2 Implementing Multiple Interfaces in C#
Code -
C# Programming
using System;
namespace CsharpInterface {
interface IPolygon {
// method without body
void calculateArea(int a, int b);
}
interface IColor {
void getColor();
}
// implements two interface
class Rectangle : IPolygon, IColor {
// implementation of IPolygon interface
public void calculateArea(int a, int b) {
int area = a * b;
Console.WriteLine("Area of Rectangle: " + area);
}
// implementation of IColor interface
public void getColor() {
Console.WriteLine("Red Rectangle");
}
}
class Program {
static void Main (string [] args) {
Rectangle r1 = new Rectangle();
r1.calculateArea(100, 200);
r1.getColor();
}
}
}Output
Area of Rectangle: 20000
Red Rectangle
Red Rectangle
#3 Using reference variable of an interface in C#
Code -
C# Programming
using System;
namespace CsharpInterface {
interface IPolygon {
// method without body
void calculateArea(int l, int b);
}
class Rectangle : IPolygon {
// implementation of methods inside interface
public void calculateArea(int l, int b) {
int area = l * b;
Console.WriteLine("Area of Rectangle: " + area);
}
}
class Program {
static void Main (string [] args) {
// using reference variable of interface
IPolygon r1 = new Rectangle();
r1.calculateArea(100, 200);
}
}
}Output
Area of Rectangle: 20000
#4 Practical Example of Interface in C#
Code -
C# Programming
using System;
namespace CsharpInterface {
interface IPolygon {
// method without body
void calculateArea();
}
// implements interface
class Rectangle : IPolygon {
// implementation of IPolygon interface
public void calculateArea() {
int l = 30;
int b = 90;
int area = l * b;
Console.WriteLine("Area of Rectangle: " + area);
}
}
class Square : IPolygon {
// implementation of IPolygon interface
public void calculateArea() {
int l = 30;
int area = l * l;
Console.WriteLine("Area of Square: " + area);
}
}
class Program {
static void Main (string [] args) {
Rectangle r1 = new Rectangle();
r1.calculateArea();
Square s1 = new Square();
s1.calculateArea();
}
}
}Output
Area of Rectangle: 2700
Area of Square: 900
Area of Square: 900
Demonstration
C# Programming Example interface