如何获取alt+tab能够切换到的上个窗口的消息？

没太看懂

可以参考这个代码：

using System;
using System.Runtime.InteropServices;

class Program
{
    // 导入必要的 Win32 API 函数
    [DllImport("user32.dll")]
    private static extern IntPtr GetForegroundWindow();

    [DllImport("user32.dll", SetLastError = true)]
    private static extern IntPtr GetWindow(IntPtr hWnd, uint uCmd);

    private const uint GW_HWNDNEXT = 2;

    static void Main()
    {
        IntPtr currentWindowHandle = GetForegroundWindow();
        IntPtr nextWindowHandle = GetWindow(currentWindowHandle, GW_HWNDNEXT);

        Console.WriteLine("当前前景窗口句柄: " + currentWindowHandle);
        Console.WriteLine("下一个窗口句柄: " + nextWindowHandle);
    }
}