A C# interfaces is defined as a syntactical contract that all the classes inheriting the interface should follow. The interface defines the ‘what’ part of the syntactical contract and the deriving classes define the ‘how’ part of the syntactical contract.
Interfaces define properties, methods, and events, which are the members of the interface. Interfaces contain only the declaration of the members. It is the responsibility of the deriving class to define the members. It often helps in providing a standard structure that the deriving classes would follow.
Declaring C# Interfaces
I It is similar to the class declaration. Interface statements are public by default. Following is an example of an interface declaration −
public interface ITransactions {
// interface members
void showTransaction();
double getAmount();
}
Example
The following example demonstrates the implementation of the above interface −
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System;
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();
}
}
}
The following result −
Transaction: 001 Date: 8/10/2012 Amount: 78900 Transaction: 002 Date: 9/10/2012 Amount: 451900
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