using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace Lambda表达式
{
    class Program
    {
        static void Main(string[] args)
        {
            //lambda表达式的演变过程
            //下面是C#1.0中创建委托实例的代码
            Func<string, int> delegatetest1 = new Func<string, int>(callbackmethod);
            //
            //C#2.0中用匿名方法来创建委托实例，此事就不需要去额外定义回调方法callbackmethod了
            Func<string, int> deledatetest2 = delegate(string text)
            {
                return text.Length;
            };
            //
            //C# 3.0中使用lamabda表达式来创建委托实例
            Func<string, int> delegatetest3 = (string text) => text.Length;
            //
            //可以省略类型参数string，从而代码再次简化
            Func<string, int> delegatetest4 = (text) => text.Length;
            //括号省略
            Func<string, int> delegatetest = text => text.Length;
            
            //调用委托
            Console.WriteLine("use lambda to retun text.length=" + delegatetest("helloworld"));
            Console.WriteLine("------------------------------------------------------------");
            //以上是lamada演变过程
            //下面是lamada在订阅事件的使用

            //定义一个按钮
            Button btn = new Button() { Text = "点击我啊" };
            btn.Click+=(sender,e)=>ReportEvent("点击按钮事件",sender,e);
            //定义窗体显示
            Form form = new Form() { Name = "在控制台创建的窗体", AutoSize = true, Controls = { btn } };
            //运行窗体
            Application.Run(form);
            Console.Read();
        }
        private static int callbackmethod(string text)
        {
            return text.Length;
        }
        private static void ReportEvent(string title, object sender, EventArgs e)
        {
            Console.WriteLine("发生的事件为:{0}", title);
            Console.WriteLine("发生事件的对象是：{0}",sender);
            Console.WriteLine("发生事件的参数是：{0}",e.GetType());
        }
    }
}