Two class inherit one interface : Interface : Class Interface C# Source Code

    

/*
C#: The Complete Reference 
by Herbert Schildt 

Publisher: Osborne/McGraw-Hill (March 8, 2002)
ISBN: 0072134852
*/
using System; 

// An encryption interface. 
public interface ICipher { 
  string encode(string str); 
  string decode(string str); 
}

/* A simple implementation of ICipher that codes 
   a message by shifting each character 1 position 
   higher.  Thus, A becomes B, and so on. */ 
class SimpleCipher : ICipher { 
     
  // Return an encoded string given plaintext. 
  public string encode(string str) { 
    string ciphertext = ""; 
 
    for(int i=0; i < str.Length; i++) 
      ciphertext = ciphertext + (char) (str[i] + 1); 
 
    return ciphertext; 
  } 
 
  // Return an decoded string given ciphertext. 
  public string decode(string str) { 
    string plaintext = ""; 
 
    for(int i=0; i < str.Length; i++) 
      plaintext = plaintext + (char) (str[i] - 1); 
 
    return plaintext; 
  } 
} 
 
/* This implementation of ICipher uses bit 
   manipulations and key. */ 
class BitCipher : ICipher { 
  ushort key; 
 
  // Specify a key when constructing BitCiphers. 
  public BitCipher(ushort k) { 
    key = k; 
  } 
     
  // Return an encoded string given plaintext. 
  public string encode(string str) { 
    string ciphertext = ""; 
 
    for(int i=0; i < str.Length; i++) 
      ciphertext = ciphertext + (char) (str[i] ^ key); 
 
    return ciphertext; 
  } 
 
  // Return an decoded string given ciphertext. 
  public string decode(string str) { 
    string plaintext = ""; 
 
    for(int i=0; i < str.Length; i++) 
      plaintext = plaintext + (char) (str[i] ^ key); 
 
    return plaintext; 
  } 
}

// Demonstrate ICipher. 
 
public class ICipherDemo { 
  public static void Main() { 
    ICipher ciphRef; 
    BitCipher bit = new BitCipher(27); 
    SimpleCipher sc = new SimpleCipher(); 
 
    string plain; 
    string coded; 
 
    // first, ciphRef refers to the simple cipher 
    ciphRef = sc; 
 
    Console.WriteLine("Using simple cipher."); 
 
    plain = "testing"; 
    coded = ciphRef.encode(plain); 
    Console.WriteLine("Cipher text: " + coded); 
 
    plain = ciphRef.decode(coded); 
    Console.WriteLine("Plain text: " + plain); 
 
    // now, let ciphRef refer to the bitwise cipher 
    ciphRef = bit; 
 
    Console.WriteLine("\nUsing bitwise cipher."); 
 
    plain = "testing"; 
    coded = ciphRef.encode(plain); 
    Console.WriteLine("Cipher text: " + coded); 
 
    plain = ciphRef.decode(coded); 
    Console.WriteLine("Plain text: " + plain); 
  } 
}