老生常谈 C# 开发 Windows 消息循环机制的原理和流程

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

class Program
{
    // 导入Windows API函数
    [DllImport("user32.dll")]
    private static extern bool GetMessage(out MSG lpMsg, IntPtr hWnd, uint wMsgFilterMin, uint wMsgFilterMax);

    [DllImport("user32.dll")]
    private static extern bool TranslateMessage([In] ref MSG lpMsg);

    [DllImport("user32.dll")]
    private static extern IntPtr DispatchMessage([In] ref MSG lpMsg);

    [DllImport("user32.dll")]
    private static extern IntPtr CreateWindowEx(
        uint dwExStyle,
        string lpClassName,
        string lpWindowName,
        uint dwStyle,
        int x,
        int y,
        int nWidth,
        int nHeight,
        IntPtr hWndParent,
        IntPtr hMenu,
        IntPtr hInstance,
        IntPtr lpParam);

    [DllImport("user32.dll")]
    private static extern bool DestroyWindow(IntPtr hWnd);

    // 定义消息结构体
    [StructLayout(LayoutKind.Sequential)]
    public struct MSG
    {
        public IntPtr hwnd;
        public uint message;
        public IntPtr wParam;
        public IntPtr lParam;
        public uint time;
        public POINT pt;
    }

    // 定义坐标结构体
    [StructLayout(LayoutKind.Sequential)]
    public struct POINT
    {
        public int X;
        public int Y;
    }

    // 定义窗口过程回调函数
    private delegate IntPtr WndProcDelegate(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);

    private static WndProcDelegate wndProc;

    // 窗口过程回调函数
    private static IntPtr WindowProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam)
    {
        switch (msg)
        {
            case WM_PAINT:
                // 处理窗口重绘消息
                Console.WriteLine("窗口重绘");
                break;

            case WM_KEYDOWN:
                // 处理键盘按下消息
                Console.WriteLine("键盘按下");
                break;

            case WM_CLOSE:
                // 处理窗口关闭消息
                DestroyWindow(hWnd);
                break;

            default:
                // 其他消息交给默认处理
                return DefWindowProc(hWnd, msg, wParam, lParam);
        }

        return IntPtr.Zero;
    }

    // 创建消息循环
    private static void CreateMessageLoop()
    {
        // 注册窗口类
        WNDCLASSEX wndClass = new WNDCLASSEX();
        wndClass.cbSize = (uint)Marshal.SizeOf(wndClass);
        wndClass.lpfnWndProc = Marshal.GetFunctionPointerForDelegate(wndProc);
        wndClass.hInstance = Marshal.GetHINSTANCE(typeof(Program).Module);
        wndClass.lpszClassName = "MyWindowClass";

        if (RegisterClassEx(ref wndClass) == 0)
        {
            throw new Exception("注册窗口类失败");
        }

        // 创建窗口
        IntPtr hWnd = CreateWindowEx(
            0,
            "MyWindowClass",
            "My Window",
            WS_OVERLAPPEDWINDOW,
            CW_USEDEFAULT, CW_USEDEFAULT, 640, 480,
            IntPtr.Zero, IntPtr.Zero, IntPtr.Zero, IntPtr.Zero);

        if (hWnd == IntPtr.Zero)
        {
            throw new Exception("创建窗口失败");
        }

        // 显示窗口
        ShowWindow(hWnd, SW_SHOWDEFAULT);

        // 进入消息循环
        MSG msg;
        while (GetMessage(out msg, IntPtr.Zero, 0, 0))
        {
            TranslateMessage(ref msg);
            DispatchMessage(ref msg);
        }

        // 销毁窗口类
        UnregisterClass("MyWindowClass", Marshal.GetHINSTANCE(typeof(Program).Module));
    }

    static void Main()
    {
        wndProc = WindowProc;
        CreateMessageLoop();
    }

    // 常量定义
    private const uint WM_PAINT = 0x000F;
    private const uint WM_KEYDOWN = 0x0100;
    private const uint WM_CLOSE = 0x0010;
    private const uint WS_OVERLAPPEDWINDOW = 0xCF0000;
    private const int CW_USEDEFAULT = unchecked((int)0x80000000);
    private const int SW_SHOWDEFAULT = 10;

    // 导入Windows API函数
    [DllImport("user32.dll")]
    private static extern short RegisterClassEx([In] ref WNDCLASSEX lpWndClass);

    [DllImport("user32.dll")]
    private static extern short UnregisterClass(string lpClassName, IntPtr hInstance);

    [DllImport("user32.dll")]
    private static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);

    [DllImport("user32.dll")]
    private static extern IntPtr DefWindowProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);

    // 定义窗口类结构体
    [StructLayout(LayoutKind.Sequential)]
    public struct WNDCLASSEX
    {
        public uint cbSize;
        public uint style;
        [MarshalAs(UnmanagedType.FunctionPtr)] public WndProcDelegate lpfnWndProc;
        public int cbClsExtra;
        public int cbWndExtra;
        public IntPtr hInstance;
        public IntPtr hIcon;
        public IntPtr hCursor;
        public IntPtr hbrBackground;
        public string lpszMenuName;
        public string lpszClassName;
        public IntPtr hIconSm;
    }
}