关于Form_load()和OnLoad()使用中的联系与区别

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

namespace OnLoadDemo
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            MessageBox.Show("Form_Load");
        }
        protected override void OnLoad(EventArgs e)
        {
            //base.OnLoad(e);
            MessageBox.Show("OnLoad");
        }
    }
}

 

 仅仅弹出“OnLoad”，Form1_Load（）函数没有加载；

现在，注释掉base.OnLoad(e);运行之后，看一下情况如何变化：

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

namespace OnLoadDemo
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            MessageBox.Show("Form_Load");
        }
        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);
            MessageBox.Show("OnLoad");
        }
    }
}

先出现From1_Load，如下

 

 点击“确定”后，紧接着弹出OnLoad

 

 综合以上两个示例：

base.onload(e);会引发事件调用Form1_Load()函数；如果重写了onload（）函数，那么基类就不会引发From1_Load()事件；

事件是由委托构成的，如果事件没有触发，则delegate.BeginInvoke()就不会运行，delegate.BeginInvoke()不运行就不触发消息传递；

因为OnShown()事件是没有windows消息的，也就进一步说明，没有base.onload(e);的话OnShown()就无法运行，具体如下

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;
using System.Windows.Forms;

namespace LifeCycleDemo
{
    class Program:Form
    {
        static void Main(string[] args)
        {
            Application.Run(new Program());
        }
        public Program()
        {
            Text = "LifeCycleDemo";
        }

        int inder = 0;

        protected override void OnLoad(EventArgs e)
        {
            //base.OnLoad(e);
            Console.WriteLine("the order of OnLoad event is {0}",++inder);
        }
        protected override void OnPaint(PaintEventArgs e)
        {
            Console.WriteLine("the order of onPaint event is {0}", ++inder);
        }
        protected override void OnShown(EventArgs e)
        {
            Console.WriteLine("the order of OnShow event is {0}", ++inder);
            MessageBox.Show("Are you ready ?");
        }
        //protected override void OnActivated(EventArgs e)
        //{
        //    Console.WriteLine("onActivated 事件的顺序是{0}", ++inder);
        //}
        //protected override void OnDeactivate(EventArgs e)
        //{
        //    Console.WriteLine("onDeactive 事件的顺序是{0}", ++inder);
        //}
        //protected override void OnFormClosed(FormClosedEventArgs e)
        //{
        //    Console.WriteLine("onFormClosed 事件的顺序是{0}", ++inder);
        //}
        //protected override void OnFormClosing(FormClosingEventArgs e)
        //{
        //    Console.WriteLine("onFormClosing 事件的顺序是{0}", ++inder);
        //}
    }
}

 

 因为注释掉了base.onload(e);所以，onshown()也没有触发；

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;
using System.Windows.Forms;

namespace LifeCycleDemo
{
    class Program:Form
    {
        static void Main(string[] args)
        {
            Application.Run(new Program());
        }
        public Program()
        {
            Text = "LifeCycleDemo";
        }

        int inder = 0;

        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);
            Console.WriteLine("the order of OnLoad event is {0}",++inder);
        }
        protected override void OnPaint(PaintEventArgs e)
        {
            Console.WriteLine("the order of onPaint event is {0}", ++inder);
        }
        protected override void OnShown(EventArgs e)
        {
            Console.WriteLine("the order of OnShow event is {0}", ++inder);
            MessageBox.Show("Are you ready ?");
        }
        //protected override void OnActivated(EventArgs e)
        //{
        //    Console.WriteLine("onActivated 事件的顺序是{0}", ++inder);
        //}
        //protected override void OnDeactivate(EventArgs e)
        //{
        //    Console.WriteLine("onDeactive 事件的顺序是{0}", ++inder);
        //}
        //protected override void OnFormClosed(FormClosedEventArgs e)
        //{
        //    Console.WriteLine("onFormClosed 事件的顺序是{0}", ++inder);
        //}
        //protected override void OnFormClosing(FormClosingEventArgs e)
        //{
        //    Console.WriteLine("onFormClosing 事件的顺序是{0}", ++inder);
        //}
    }
}

启用base.onload(e);后，onshown()就会引起触发并运行；