C# 委托、lambda表达式和事件

什么是委托？委托就是持有一个或多个方法的对象，并且该对象可以执行，可以传递。

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

namespace ConsoleApplication1
{
    class Program
    {
        // 定义委托事件
        delegate void ActCute();
        static void Main(string[] args)
        {
            ActCute del = null;
            Dog dog1 = new Dog("dog");
            Cat cat1 = new Cat("cat");
            // 委托事件的添加
            del = dog1.WagTail;
            del += cat1.InnocentLook;
            // 定义lambda 表达式
            del += () =>
            {
                Console.WriteLine("这是lambda表达式定义的方法!!!");
            };
            // 按照添加的顺序依次调用
            del();
        }
        public class Dog
        {
            private string Name;
            public Dog(string name)
            {
                Name = name;
            }
            public void WagTail()
            {
                Console.WriteLine(Name + "正在摇尾巴...");
            }
        }
        public class Cat
        {
            private string Name;
            public Cat(string name)
            {
                Name = name;
            }
            public void InnocentLook()
            {
                Console.WriteLine(Name + "正在摆弄无辜表情...");
            }
        }
    }
}

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

namespace ConsoleApplication2
{
    class Program
    {
        delegate void Func1();
        // 使用方法
        public static void Aminal()
        {
            Console.WriteLine("我是一只动物...");
        }
        public static void Plant()
        {
            Console.WriteLine("我是一棵植物...");
        }
        static void Main(string[] args)
        {
            Func1 myfunc1;
            myfunc1 = new Func1(Aminal);
            myfunc1 += new Func1(Plant);
            myfunc1();

        }
    }
}

委托是一个类型，事件是委托的一个特殊实例。

定义一个委托实例是不完全的，可以被外部的类调用内部的委托；事件可以在外部定义，但是触发事件是在内部。所以相对于普通的委托，事件是安全的。

事件：一种封装受限制的委托。

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Client1 c1 = new Client1();
            Client1 c2 = new Client1();
            // 绑定委托
            Dog.NewDog += c1.WangADog;
            Dog.NewDog += c2.WangADog;
            Dog dog1 = new Dog("jack");
        }
        public class Dog
        {
            private string Name;
            public delegate void Handler();  // 定义委托类型
            public static event Handler NewDog;  // 在委托事情上定义事件
            public Dog(string name)
            {
                Name = name;
                if (NewDog != null)
                {
                    NewDog();
                }
            }
            public void WagTail()
            {
                Console.WriteLine(Name + "正在摇尾巴...");
            }
        }
        class Client1
        {
            public void WangADog()
            {
                Console.WriteLine("我想要一条狗!!!");
            }
        }
    }
}

2019-7-29

委托和事件在窗体之间的应用：

委托：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace 窗体之间的传参
{
    public partial class ParentForm : Form
    {
        public Action<string> ChildFrm { get; set; }  // 定义一个委托
        public ParentForm()
        {
            InitializeComponent();
        }

        private void ParentForm_Load(object sender, EventArgs e)
        {
            ChildForm frm = new ChildForm();  // 初始化子窗体
            ChildFrm += frm.SetText;  // 绑定事件
            frm.Show();
        }

        private void Btn_Send_Click(object sender, EventArgs e)
        {
            ChildFrm(this.TB_Msg.Text);
        }
    }
}
======================================================
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace 窗体之间的传参
{
    public partial class ChildForm : Form
    {
        public ChildForm()
        {
            InitializeComponent();
        }

        private void ChildForm_Load(object sender, EventArgs e)
        {

        }
        public void SetText(string text)
        {
            this.TB_Msg.Text = text;
        }
    }
}

事件：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace 窗体之间的传参
{
    public partial class ParentForm : Form
    {
        public event EventHandler ChildFrmEvent;  // 定义一个事件
        public ParentForm()
        {
            InitializeComponent();
        }

        private void ParentForm_Load(object sender, EventArgs e)
        {
            ChildForm frm = new ChildForm();  // 初始化子窗体
            ChildFrmEvent += frm.FrmEvent;  // 绑定子窗体里面的事件
            frm.Show();  // 显示
        }

        private void Btn_Send_Click(object sender, EventArgs e)
        {
            ChildFrmEvent(this, new NewEventArgsClass() { Text = this.TB_Msg.Text });
        }
    }
}
===================================================================
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace 窗体之间的传参
{
    public partial class ChildForm : Form
    {
        public ChildForm()
        {
            InitializeComponent();
        }

        private void ChildForm_Load(object sender, EventArgs e)
        {
        }
        public void FrmEvent(object sender, EventArgs e)
        {
            NewEventArgsClass args = e as NewEventArgsClass;
            TB_Msg.Text = args.Text;
        }
    }
}
===================================================================================================

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

namespace 窗体之间的传参
{
　　class NewEventArgsClass:EventArgs
　　{
　　　　public string Text { get; set; }
　　}
}

 管家解耦父子窗体(发布订阅模式的非委托实现)：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace 管家解耦父子窗体
{
    public partial class MasterForm : Form
    {
        public MasterForm()
        {
            InitializeComponent();
        }

        private void MasterForm_Load(object sender, EventArgs e)
        {
            // 启动父子窗体
            ParentForm PFrm = new ParentForm();
            ChildForm CFrm = new ChildForm();
            PFrm.ChildList = new List<TotalInterface>();
            PFrm.ChildList.Add(CFrm);
            PFrm.Show();
            CFrm.Show();
        }
    }
}
=======================================================================
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace 管家解耦父子窗体
{
    public partial class ParentForm : Form
    {
        public List<TotalInterface> ChildList { get; set; }
        public ParentForm()
        {
            InitializeComponent();
        }

        private void ParentForm_Load(object sender, EventArgs e)
        {

        }

        private void Btn_Send_Click(object sender, EventArgs e)
        {
            if (ChildList == null) return;
            foreach(TotalInterface item in ChildList)
            {
                item.SetText(this.TB_Msg.Text);
            }
        }
    }
}
=============================================================
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace 管家解耦父子窗体
{
    public partial class ChildForm : Form,TotalInterface
    {
        public ChildForm()
        {
            InitializeComponent();
        }

        public void SetText(string text)
        {
            this.TB_Msg.Text = text;
        }

        private void ChildForm_Load(object sender, EventArgs e)
        {

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

namespace 管家解耦父子窗体
{
    // 定义接口
    public interface TotalInterface
    {
        void SetText(string text);
    }
}