C# Example of Interface

Example of Interface in C# Language:

Define Interface:

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace InterfaceApplication

{

   public interface ITransactions

   {

      // interface members

      void showTransaction();

      double getAmount();

   }

   public class Transaction : ITransactions

   {

      private string tCode;

      private string date;

      private double amount;

      public Transaction()

      {

         tCode = " ";

         date = " ";

         amount = 0.0;

      }

      public Transaction(string c, string d, double a)

      {

         tCode = c;

         date = d;

         amount = a;

      }

      public double getAmount()

      {

         return amount;

      }

      public void showTransaction()

      {

         Console.WriteLine("Transaction: {0}", tCode);

         Console.WriteLine("Date: {0}", date);

         Console.WriteLine("Amount: {0}", getAmount());

      }

   }

   class Tester

   {

      static void Main(string[] args)

      {

         Transaction t1 = new Transaction("001", "8/10/2012", 78900.00);

         Transaction t2 = new Transaction("002", "9/10/2012", 451900.00);

         t1.showTransaction();

         t2.showTransaction();

         Console.ReadKey();

      }

   }

}

Result when use this Interface:

When This code is compiled and executed, it produces the following result:

Transaction: 001

Date: 8/10/2012

Amount: 78900

Transaction: 002

Date: 9/10/2012

Amount: 451900

DIFFERENCE BETWEEN AN ABSTRACT CLASS AND AN INTERFACE IN C#:

An Abstract class doesn't provide full abstraction but an interface does provide full abstraction; i.e. both a declaration and a definition is given in an abstract class but not so in an interface.

Using Abstract we cannot achieve multiple inheritances but using an Interface we can achieve multiple inheritances.

We cannot declare a member field in an Interface.

We cannot use any access modifier i.e. public, private, protected, internal etc. because within an interface by default everything is public.

An Interface member cannot be defined using the keyword static, virtual, abstract or sealed.