委托可以把部分代码孤立出来写成一个函数，达到灵活应用的目的。在一些框架中有较多的应用。

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

namespace CSharpAdvancedDelegate
{
    /// <summary>
    /// 1  委托是一个引用类型，其实它是一个类，保存方法的指针，他指向一个方法，当我们调用委托
    /// 的时候这个方法就立即被执行。
    /// </summary> 
    class Program
    {
        static void Main(string[] args)
        {           
            Console.WriteLine("==================================");
            List<LearnLegegateStu> learnLegegateStus = new List<LearnLegegateStu>();
            learnLegegateStus.Add(new LearnLegegateStu() { Id = 1, StuName = "tom", Price = 199 });
            learnLegegateStus.Add(new LearnLegegateStu() { Id = 2, StuName = "cat", Price = 699 });
            learnLegegateStus.Add(new LearnLegegateStu() { Id = 4, StuName = "dog", Price = 499 });
            learnLegegateStus.Add(new LearnLegegateStu() { Id = 3, StuName = "pig", Price = 599 });
            IsLeearnStu isLeearnStu = new IsLeearnStu(GetStu);//创委托实例,实现方法与委托关联
            LearnLegegateStu.CSharpStu(learnLegegateStus,isLeearnStu);  //由于是静态方法是类名.静态方法名+参数; 


            Console.Read();
        }

   //委托也是一个类，要实例化，在实例化时要与函数进行关联；
        public static bool GetStu(LearnLegegateStu learnLegegateStu)
        {
            if (learnLegegateStu.Price>=599)
            {
                return true;
            }
            else
            {
                return false;
            }
        }       
    }

    delegate bool IsLeearnStu(LearnLegegateStu learnLegegateStu); //定义委托
    class LearnLegegateStu
    {
        public int Id { get; set; }
        public string StuName { get; set; }
        public int Price { get; set; }
        public static void CSharpStu(List<LearnLegegateStu> learnLegegateStus,IsLeearnStu isLeearnStu)
        {
            foreach (LearnLegegateStu learnLegegateStu in learnLegegateStus)
            {                
                if (isLeearnStu(learnLegegateStu))
                {
                    Console.WriteLine(learnLegegateStu.StuName+"是学员");
                }
            }
        }
    }
}