接口有什么用，请用代码举例说明

参考
下面的示例演示了接口实现。在此例中，接口 IPoint 包含属性声明，后者负责设置和获取字段的值。Point 类包含属性实现。
// keyword_interface_2.cs
// Interface implementation
using System;
interface IPoint
{
   // Property signatures:
   int x
   {
      get;
      set;
   }   int y
   {
      get;
      set;
   }
}class Point : IPoint
{
   // Fields:
   private int _x;
   private int _y;   // Constructor:
   public Point(int x, int y)
   {
      _x = x;
      _y = y;
   }   // Property implementation:
   public int x
   {
      get
      {
         return _x;
      }      set
      {
         _x = value;
      }
   }   public int y
   {
      get
      {
         return _y;
      }
      set
      {
         _y = value;
      }
   }
}class MainClass
{
   static void PrintPoint(IPoint p)
   {
      Console.WriteLine("x={0}, y={1}", p.x, p.y);
   }   static void Main()
   {
      Point p = new Point(2, 3);
      Console.Write("My Point: ");
      PrintPoint(p);
   }
}

using System;
interface IPoint
{
   // Property signatures:
   int x
   {
      get;
      set;
   }   int y
   {
      get;
      set;
   }
}class Point : IPoint
{
   // Fields:
   private int _x;
   private int _y;   // Constructor:
   public Point(int x, int y)
   {
      _x = x;
      _y = y;
   }   // Property implementation:
   public int x
   {
      get
      {
         return _x;
      }      set
      {
         _x = value;
      }
   }   public int y
   {
      get
      {
         return _y;
      }
      set
      {
         _y = value;
      }
   }
}class MainClass
{
   static void PrintPoint(IPoint p)
   {
      Console.WriteLine("x={0}, y={1}", p.x, p.y);
   }   static void Main()
   {
      Point p = new Point(2, 3);
      Console.Write("My Point: ");
      PrintPoint(p);
   }
}

using System;interface I1
{
  void do();
}
class class1:I1
{
   public void do()
   {
      Console.WriteLine("我是第一个人");
   }
}
class class2:I1
{
   public void do()
   {
      Console.WriteLine("第二");
   }
}class MainClass
{
  static void PrintPoint(IPoint p)
  {
      Console.WriteLine("我有什么用？");
  }   static void Main()
  {
     I1 obj_I1  =new class1();
     obj_I1.do();
     obj_I1 = new class2();
     obj_I1.do();
  }

class MainClass
{
  static void PrintPoint(IPoint p)
  {
      Console.WriteLine("我有什么用？");
  }
// 是引用楼上几层那代码。忽略吧

接口就是主机上的usb插槽，你能插鼠标也可以插U盘还可以插mpn,手机，摄像头......

一句话：接口就是为了减少变化对程序的影响。interface IExecutor{
Execute();
}这个执行器接口可以实现为：
class SqlExecutor:IExecutor
或者
class FileExecutor:IExecutor他们都能执行，但是可能一个事执行SQL另一个则是执行文件。对于框架设计来说这点很重要，框架只需要知道我需要执行，但是到底怎么执行则有实现者来提供。

接口就是，我用的人必须会干接口规定的事情，如会上CSDN

来看一个使用接口的实例，创建一个接口Icipher，用来指定一个加密和字符串的方法。接口定义：view plaincopy to clipboardprint?
namespace Cipher
{
    public interface ICipher
    {
        //加密
        string encode(string str);
        //解密
        string decode(string str);
    }
}
namespace Cipher
{
    public interface ICipher
    {
        //加密
        string encode(string str);
        //解密
        string decode(string str);
    }
}下面两个类实现了Icipher。view plaincopy to clipboardprint?
/*简单的易位代码，通过将每个字符都向高位一定一位来加密字符串*/
    public class SimpleCipher:ICipher
    {
        public string encode(string str)
        {
            string ciphertext = "";
            for (int i = 0; i < str.Length; ++i)
            {
                Console.WriteLine(i.ToString()+"    "+(str[i] + 1).ToString());
                ciphertext = ciphertext + (char)(str[i] + 1);
            }
            return ciphertext;
        }
        public string decode(string str)
        {
            string plaintext = "";
            for (int i = 0; i < str.Length; ++i)
            {
                plaintext = plaintext + (char)(str[i] - 1);
            }
            return plaintext;
        }
/*简单的易位代码，通过将每个字符都向高位一定一位来加密字符串*/
    public class SimpleCipher:ICipher
    {
        public string encode(string str)
        {
            string ciphertext = "";
            for (int i = 0; i < str.Length; ++i)
            {
                Console.WriteLine(i.ToString()+"    "+(str[i] + 1).ToString());
                ciphertext = ciphertext + (char)(str[i] + 1);
            }
            return ciphertext;
        }
        public string decode(string str)
        {
            string plaintext = "";
            for (int i = 0; i < str.Length; ++i)
            {
                plaintext = plaintext + (char)(str[i] - 1);
            }
            return plaintext;
        } view plaincopy to clipboardprint?
/*通过将每个字符与一个16位的密钥进行XOR（异或）运算加密字符串*/
    public class BitCipher : ICipher
    {
        ushort key;
        public BitCipher(ushort k)
        {
            key = k;
        }
        public string encode(string str)
        {
            string ciphertext = "";
            for (int i = 0; i < str.Length; ++i)
            {
                ciphertext = ciphertext + (char)(str[i] ^ key);
            }
            return ciphertext;
        }
        public string decode(string str)
        {
            string plaintext = "";
            for (int i = 0; i < str.Length; ++i)
            {
                plaintext = plaintext + (char)(str[i] ^ key);
            }
            return plaintext;
        }
/*通过将每个字符与一个16位的密钥进行XOR（异或）运算加密字符串*/
    public class BitCipher : ICipher
    {
        ushort key;
        public BitCipher(ushort k)
        {
            key = k;
        }
        public string encode(string str)
        {
            string ciphertext = "";
            for (int i = 0; i < str.Length; ++i)
            {
                ciphertext = ciphertext + (char)(str[i] ^ key);
            }
            return ciphertext;
        }
        public string decode(string str)
        {
            string plaintext = "";
            for (int i = 0; i < str.Length; ++i)
            {
                plaintext = plaintext + (char)(str[i] ^ key);
            }
            return plaintext;
        } 虽然SimpleCipher和BitCipher在实现上完全不同，但他们都实现了ICipher接口。下面示范了两个类的用法：view plaincopy to clipboardprint?
static void Main(string[] args)
        {
            ICipher ciphRef;
            BitCipher bit = new BitCipher(27);
            SimpleCipher sc = new SimpleCipher();

            string plain;
            string coded;

            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);




            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);
        }
static void Main(string[] args)
        {
            ICipher ciphRef;
            BitCipher bit = new BitCipher(27);
            SimpleCipher sc = new SimpleCipher();            string plain;
            string coded;            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);
            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);
        } 创建加密接口的好处在于，无论加密方法如何实现，只要类中实现了该接口，就可以以相同的方式访问它。
我的博客：http://blog.csdn.net/kdmhh/archive/2009/08/23/4474387.aspx

调试易

接口有什么用，请用代码举例说明

解决方案 »