c#利用ApplicationContext类 同时启动双窗体的实现

Application类（位于System.Windows.Forms命名空间）公开了Run方法，可以调用该方法来调度应用程序进入消息循环。Run方法有三个重载

1、第一个重载版本不带任何参数，比较少使用

2、static void Run(System.Windows.Forms.Form mainForm)  调用这个重载，只需要吧希望作为主窗口的Form实例（包括从Form类派生的类）传递给mianForm参数即可。一旦mainForm关闭，整个消息循环就会退出，Run方法返回，应用程序就会退出。

3、static void Run(System.Windows.Forms.ApplicationContext context) 这是Run方法中重载最灵活的。通常的做法是从ApplicationContext类派生，并写入实现代码。ApplicationContext类也允许设置一个Form实例制作为主窗口，也可以不设置主窗口。这个Run方法会在ApplicationContext对象进行消息循环。调用ApplicationContext类的ExitThread方法会导致ApplicationContext上的消息循环终止。

手动创建一个类：产生三个窗口，只有把三个窗口全部关闭程序才终止运行（基于第三种Run方法）

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

//从ApplicationContext派生一个类出来，
public class MyApplication : ApplicationContext
{

    static int WindowsCount;//用于记录窗口个数
    private Form Windows1, Windows2, Windows3;//申请三个Form窗口  private只限于本类成员访问

    //构造函数，分别实例化三个窗口
    public MyApplication()
    {
        WindowsCount = ;
        /*实例化Windows1*/
        Windows1 = new Form();
        Windows1.Text = "窗口1";
        Windows1.Size = new System.Drawing.Size(, );
        Windows1.Location = new System.Drawing.Point(, );
        Windows1.Name = "Form1";
        Windows1.FormClosed += OnMainFormClosed;//处理事件（窗口关闭的处理事件）
        WindowsCount += ;//窗口总数加一

        Windows2 = new Form();
        Windows2.Text = "窗口2";
        Windows2.Size = new System.Drawing.Size(, );
        Windows2.Location = new System.Drawing.Point(, );
        Windows2.Name = "Form2";
        Windows2.FormClosed += OnMainFormClosed;//处理事件（窗口关闭的处理事件）
        WindowsCount += ;//窗口总数加一

        Windows3 = new Form();
        Windows3.Text = "窗口3";
        Windows3.Size = new System.Drawing.Size(, );
        Windows3.Location = new System.Drawing.Point(, );
        Windows3.Name = "Form3";
        Windows3.FormClosed += OnMainFormClosed;//处理事件（窗口关闭的处理事件）
        WindowsCount += ;//窗口总数加一

        //显示3个窗口
        Windows1.Show();
        Windows2.Show();
        Windows3.Show();      

    }
    private void OnMainFormClosed(object sender,FormClosedEventArgs e)
    {
        WindowsCount -= ;
        if (WindowsCount == )
            ExitThread();//调用ExitThead终止消息循环

    }

}
namespace application1
{
    static class Program
    {
        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new MyApplication());
        }
    }
}

出处：https://www.cnblogs.com/hjxzjp/p/7674300.html

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下面的代码示例显示两个窗体，并在两个窗体都关闭时退出应用程序。在应用程序启动和退出时，它会记住每个窗体的位置。此示例演示如何使用 ApplicationContext 和 Application.Run(context) 方法在启动应用程序时显示多个窗体。

类 MyApplicationContext 从 ApplicationContext 继承，并跟踪每个窗体关闭的时间，然后在这两个窗体均关闭时退出当前线程。该类为用户存储每个窗体的位置。窗体位置数据存储在标题为 Appdata.txt 的文件中，该文件在 UserAppDataPath 确定的位置中创建。

给定 ApplicationContext 的情况下，Main 方法调用 Application.Run(context) 启动应用程序。

using System;
using System.Drawing;
using System.Windows.Forms;
using System.ComponentModel;
using System.Text;
using System.IO;

namespace ScreenSplit
{
    static class Program
    {
        // 初始化窗体1大小及标题文本
        public class AppForm1 : System.Windows.Forms.Form
        {
            public AppForm1()
            {
                Screen screen = Screen.FromRectangle(new Rectangle(0, 0, 0, 0));
                this.Size = new System.Drawing.Size(screen.WorkingArea.Width / 2, screen.WorkingArea.Height);
                this.Text = "AppForm1";
            }
        }

// 初始化窗体2大小及标题文本
        public class AppForm2 : System.Windows.Forms.Form
        {
            public AppForm2()
            {
                Screen screen = Screen.FromRectangle(new Rectangle(0, 0, 0, 0));
                this.Size = new System.Drawing.Size(screen.WorkingArea.Width / 2, screen.WorkingArea.Height);
                this.Text = "AppForm2";
            }
        }

// 利用ApplicationContext类处理程序的启动、关闭
        class MyApplicationContext : ApplicationContext
        {

private int formCount;
            private AppForm1 form1;
            private AppForm2 form2;

private Rectangle form1Position;
            private Rectangle form2Position;

private FileStream userData;

private MyApplicationContext()
            {
                formCount = 0;

// 应用程序退出
                Application.ApplicationExit += new EventHandler(this.OnApplicationExit);

try
                {
                    // 在用户目录使用appdata.txt文件保存窗体退出时的位置与大小
                    userData = new FileStream(Application.UserAppDataPath + "//appdata.txt", FileMode.OpenOrCreate);

}
                catch (IOException e)
                {
                    // 程序退出时异常处理.
                    MessageBox.Show("An error occurred while attempting to show the application." +
                                    "The error is:" + e.ToString());

// 退出当前主线程
                    ExitThread();
                }

//窗体关闭
                form1 = new AppForm1();
                form1.Closed += new EventHandler(OnFormClosed);
                form1.Closing += new CancelEventHandler(OnFormClosing);
                formCount++;

form2 = new AppForm2();
                form2.Closed += new EventHandler(OnFormClosed);
                form2.Closing += new CancelEventHandler(OnFormClosing);
                formCount++;

// 从文件中读取保存窗体位置与大小的参数
                if (ReadFormDataFromFile())
                {
                    Screen screen = Screen.FromRectangle(new Rectangle(0, 0, 0, 0));
                    form1.Top = 0; form1.Left = 0;
                    form2.Top = 0; form2.Left = screen.WorkingArea.Width / 2;
                    form1.StartPosition = FormStartPosition.Manual;
                    form2.StartPosition = FormStartPosition.Manual;

form1.Bounds = form1Position;
                    form2.Bounds = form2Position;
                }

// 显示双窗体
                form1.Show();
                form2.Show();
            }

private void OnApplicationExit(object sender, EventArgs e)
            {
                // 保存窗体位置与大小
                WriteFormDataToFile();

try
                {
                    // 忽略窗体关闭时可能出现的错误
                    userData.Close();
                }
                catch { }
            }

private void OnFormClosing(object sender, CancelEventArgs e)
            {
                // 保存窗体位置与大小
                if (sender is AppForm1)
                    form1Position = ((Form)sender).Bounds;
                else if (sender is AppForm2)
                    form2Position = ((Form)sender).Bounds;
            }

private void OnFormClosed(object sender, EventArgs e)
            {
                // 关闭所有窗体，退出主线程
                formCount--;
                if (formCount == 0)
                {
                    ExitThread();
                }
            }

private bool WriteFormDataToFile()
            {
                // 保存窗体位置与大小到用户文件
                UTF8Encoding encoding = new UTF8Encoding();

RectangleConverter rectConv = new RectangleConverter();
                String form1pos = rectConv.ConvertToString(form1Position);
                String form2pos = rectConv.ConvertToString(form2Position);

byte[] dataToWrite = encoding.GetBytes("~" + form1pos + "~" + form2pos);

try
                {
                    userData.Seek(0, SeekOrigin.Begin);
                    userData.Write(dataToWrite, 0, dataToWrite.Length);
                    userData.Flush();

userData.SetLength(dataToWrite.Length);
                    return true;

}
                catch
                {
                    return false;
                }

}

private bool ReadFormDataFromFile()
            {
                // 从文件中读取窗体大小与位置
                UTF8Encoding encoding = new UTF8Encoding();
                String data;

if (userData.Length != 0)
                {
                    byte[] dataToRead = new Byte[userData.Length];

try
                    {
                        userData.Seek(0, SeekOrigin.Begin);
                        userData.Read(dataToRead, 0, dataToRead.Length);

}
                    catch (IOException e)
                    {
                        String errorInfo = e.ToString();
                        return false;
                    }
                   
                    data = encoding.GetString(dataToRead);

try
                    {
                        // 转换数据文件为 rectangles
                        RectangleConverter rectConv = new RectangleConverter();
                        String form1pos = data.Substring(1, data.IndexOf("~", 1) - 1);

form1Position = (Rectangle)rectConv.ConvertFromString(form1pos);

String form2pos = data.Substring(data.IndexOf("~", 1) + 1);
                        form2Position = (Rectangle)rectConv.ConvertFromString(form2pos);

return true;

}
                    catch
                    {
                        return false;
                    }

}
                else
                {
                    // 无数据文件时，缺省窗体位置与大小
                    return false;
                }
            }

[STAThread]
            static void Main(string[] args)
            {
                MyApplicationContext context = new MyApplicationContext();
                Application.Run(context);
            }
        }

}
}

//以上代码保存成Program.cs，修改form名称后可以直接使用。源自MSDN，稍作修改

出处：https://blog.csdn.net/guohu99/article/details/5115757