委托学习小记(1)

　　时间越长越感觉自己学习的只是还是太少啊~，最近看了Head First这本书（好书啊有木有），这本书里面有个装饰者模式，用到了委托...突然想起来~以前一直用过，但是具体为什么用也没仔细想过，以前看了很多 网上的学习资料说委托，MSDN上的专业资料可能写的很全但有的人会感觉太抽象。

　　所谓委托：delegate 是一种可用于封装命名或匿名方法的引用类型。委托类似于 C++ 中的函数指针；但是，委托是类型安全和可靠的。其实简单的说在我看来，委托现在给我带来的好处在运行期可以动态改变你要处理的东西，委托里面的参数其实传送的就是方法引用，把方法名当参数传，当然必须是保证返回值和方法签名是一样的~

　　下面是一部分简单的小例子，其实委托没我们想象的那么复杂

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace DavidTest
{
    public class Delegatebase
    {
        public delegate double CalculateMethod(double firstParam, double secondParam);

        /// <summary>
        /// Add Method
        /// </summary>
        /// <param name="first_param"></param>
        /// <param name="second_param"></param>
        /// <returns></returns>
        public static double Plus(double first_param, double second_param)
        {
            return first_param + second_param;
        }

        /// <summary>
        /// Minus Method
        /// </summary>
        /// <param name="first_param"></param>
        /// <param name="second_param"></param>
        /// <returns></returns>
        public static double Minus(double first_param, double second_param)
        {
            return first_param - second_param;
        }

        /// <summary>
        /// Mutiply Method
        /// </summary>
        /// <param name="first_param"></param>
        /// <param name="second_param"></param>
        /// <returns></returns>
        public static double Mutiply(double first_param, double second_param)
        {
            return first_param * second_param;
        }

        /// <summary>
        /// Divide Method
        /// </summary>
        /// <param name="first_param"></param>
        /// <param name="second_param"></param>
        /// <returns></returns>
        public static double Divide(double first_param, double second_param)
        {
            return second_param == 0 ? 0 : first_param / second_param;
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace DavidTest
{
    class Program
    {
        static void Main(string[] args)
        {
            #region 委托测试

            Delegatebase.CalculateMethod delegatePlus = new Delegatebase.CalculateMethod(Delegatebase.Plus);
            Delegatebase.CalculateMethod delegateMinus = new Delegatebase.CalculateMethod(Delegatebase.Minus);
            Delegatebase.CalculateMethod delegateMutiply = new Delegatebase.CalculateMethod(Delegatebase.Mutiply);
            Delegatebase.CalculateMethod delegateDivide = new Delegatebase.CalculateMethod(Delegatebase.Divide);

            Console.WriteLine("Plus Result: {0}", delegatePlus(1,2));
            Console.WriteLine("Minus Result: {0}", delegateMinus(1, 2));
            Console.WriteLine("Mutiply Result: {0}", delegateMutiply(1, 2));
            Console.WriteLine("Divide Result: {0}", delegateDivide(1, 2));

            #endregion

            Console.ReadLine();
        }
    }
}