在.NET Framework 中包含一种称作代理的机制（delegate），它类似于C/C++的函数指针，但它是面向对象的和类型安全的。
在c#代理同类和接口一样，也是一种引用类型，用户可以使用代理封装一个具有特定参数和返回类型的的方法，包括静态方法和实例方法，代理是实现.NET Framework中事件处理机制的基础。
代理的声明实际上定义了一个从System.MulticastDelegate类派生的类，这个类是由C#编译器根据代理的声明语句自动生成的。
主要有两个：
public void virtual Invoke(object value ,int32 item,Int32 numItems);//这个方法用来调用代理实例所封装的方法
public virtual IAsyncResult BeginInvoke(object value,int32 item,int32 numItems,AsyncCallback callback,Object object);
public virtual void EndInvoke(IAsyncresult result);
////////////////上面两个方法是用来执行异步调用
下面看个小例字（注：本人不善意写注释
using System;
using System.Collections.Generic;
using System.Text;
using System.Collections;
using Bookstore;
namespace Bookstore
{
public struct Book
{
public string Title;
public string Author;
public decimal Price;
public bool Paperback;
//构造函数
public Book(string title, string author, decimal price, bool paperBack)
{
Title = title;
Author = author;
Price = price;
Paperback = paperBack;
}
}
public delegate void processBookDelegate(Book book);
/// <summary>
///
/// </summary>
public class BookDB
{
ArrayList list = new ArrayList();
public void AddBook(string title, string author, decimal price, bool pagerBack)
{
list.Add(new Book(title, author, price, pagerBack));
}
public void ProcessPaperbackBooks(processBookDelegate processBook)
{
foreach (Book b in list)
{
if (b.Paperback)
processBook(b);
}
}
}
}
namespace BookTestClient
{
using Bookstore;
//
class PriceTotaller
{
int countBooks = 0;
decimal priceBooks = 0.0m;
internal void AddBookTotal(Book book)
{
countBooks += 1;
priceBooks += book.Price;
}
internal decimal AveragePrice()
{
return priceBooks / countBooks;
}
}
class Test
{
static void PrintTitle(Book b)
{
Console.WriteLine("{0}", b.Title);
}
static void Main(string[] args)
{
BookDB bookDB = new BookDB();
AddBooks(bookDB);
//
Console.WriteLine("Paperback Book Titles:");
bookDB.ProcessPaperbackBooks(new processBookDelegate(PrintTitle));
//
PriceTotaller totaller = new PriceTotaller();
//
bookDB.ProcessPaperbackBooks(new processBookDelegate(totaller.AddBookTotal));
Console.WriteLine("Average Paperback Book Price :${0:#.##}", totaller.AveragePrice());
}
static void AddBooks(BookDB bookDB)
{
bookDB.AddBook("The c Programming Language", "Brian W. Kernighan and Dennis M. Ritchie", 111.95m, true);
bookDB.AddBook("The Unicode Standard 2.0 ", "The Unicode Consortium", 311.95m, true);
bookDB.AddBook("The ms_dos Encyclopedia", "Ray Duncan", 1211.95m,false);
bookDB.AddBook("Dogbert 's Clues for the clueless", "Scott Adams", 12.00m, true);
}
}
}