Winforms:有没有一种方法可以在我的应用程序中打开表单时得到通知?

你可以用一个 MessageFilter 并监视WM_SHOWWINDOW和WM_CLOSE消息。

https://blogs.msdn.microsoft.com/calvin_hsia/2016/11/30/its-easy-to-use-windows-hooks-even-from-c/

下面是在窗体打开或关闭时写入控制台的代码。

using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace WindowsFormsApp1
{
    class Form1 : Form
    {
        public Form1()
        {
            var newWindowBtn = new Button { Text = "New Window" };
            newWindowBtn.Click += (s, e) => new Form { Text = Guid.NewGuid().ToString() }.Show(this);
            Controls.Add(newWindowBtn);
        }
    }

    static class NativeMethods
    {
        [StructLayout(LayoutKind.Sequential)]
        public struct CWPSTRUCT
        {
            public IntPtr lparam;
            public IntPtr wparam;
            public int message;
            public IntPtr hwnd;
        }

        public delegate IntPtr CBTProc(int code, IntPtr wParam, IntPtr lParam);

        public enum HookType
        {
            WH_CALLWNDPROC = 4,
        }

        [DllImport("user32.dll")]
        [return: MarshalAs(UnmanagedType.Bool)]
        public static extern bool UnhookWindowsHookEx(IntPtr hookPtr);

        [DllImport("kernel32.dll")]
        public static extern uint GetCurrentThreadId();

        [DllImport("user32.dll")]
        public static extern IntPtr CallNextHookEx(IntPtr hookPtr, int nCode, IntPtr wordParam, IntPtr longParam);

        [DllImport("user32.dll")]
        public static extern IntPtr SetWindowsHookEx(HookType hookType, CBTProc hookProc, IntPtr instancePtr, uint threadID);
    }

    static class Program
    {
        [STAThread]
        static void Main()
        {
            var hook = NativeMethods.SetWindowsHookEx(NativeMethods.HookType.WH_CALLWNDPROC, Callback, IntPtr.Zero, NativeMethods.GetCurrentThreadId());
            try
            {
                Application.Run(new Form1());
            }
            finally
            {
                NativeMethods.UnhookWindowsHookEx(hook);
            }
        }

        static IntPtr Callback(int code, IntPtr wParam, IntPtr lParam)
        {
            var msg = Marshal.PtrToStructure(lParam);
            if (msg.message == 0x0018)//WM_SHOWWINDOW
            {
                var form = Control.FromHandle(msg.hwnd) as Form;
                if (form != null)
                {
                    Console.WriteLine($"Opened form [{form.Handle}|{form.Text}]");
                }
            }
            if (msg.message == 0x0010)//WM_CLOSE
            {
                var form = Control.FromHandle(msg.hwnd) as Form;
                if (form != null)
                {
                    Console.WriteLine($"Closed form [{form.Handle}|{form.Text}]");
                }
            }
            return NativeMethods.CallNextHookEx(IntPtr.Zero, code, wParam, lParam);
        }
    }
}

您可以定义自己的类型 FooForm Form . 在 ,激发一个静态定义的 FormOpened 事件

食品形式 而不是 形式 . 每次打开一个窗体时都会触发该事件。

我最终构建了一个窗口管理器类,当创建一个新表单时,它会将自己添加到窗口管理器的集合中。您可以将此功能封装在一个基表单类中,这样您就不必记得这样做了。然后,您可以在窗口管理器类中创建事件来通知您类似的情况。您还可以在manager类中查询窗口集合。然后,我使用这个类将构建打开窗口菜单的功能整合到实用程序类中。

一个简单的全局窗体计数器:

public static class AppForms
{
    public static int OpenForms { get; private set; }
    public static event EventHandler FormShown;
    public static event EventHandler FormClosed;
    public static void Watch(Form form)
    {
        form.Shown += (sender, e) => { OpenForms++; FormShown?.Invoke(sender, e); };
        form.Closed += (sender, e) => { OpenForms--; FormClosed?.Invoke(sender, e); };
    }
}

下一步是对项目进行项目宽度搜索 InitializeComponent

InitializeComponent();
AppForms.Watch(this);

最后订阅全球活动 FormShown 和 FormClosed 在主窗体的构造函数中。

AppForms.FormShown += (sender, e) =>
{
    this.Text = $"OpenForms: {AppForms.OpenForms}";
};
AppForms.FormClosed += (sender, e) =>
{
    this.Text = $"OpenForms: {AppForms.OpenForms}";
};

您不必担心表单不会因为事件订阅而被垃圾收集。班级 AppForms Only the publishers keep references of subscribers .