WinForms/WPF透明背景子窗体嵌入第三方程序后不可见求助

我在WinForms中通过以下代码将窗体设置为第三方父窗体的子窗体：

SetParent(guestHandle, hostHandle); 
SetWindowLongPtr(guestHandle, GWL_STYLE, GetWindowLong(guestHandle, GWL_STYLE) | WS_CHILD);

此时窗体可正常嵌入父窗口，但为其设置透明背景后，子窗体完全无法显示，功能全部失效。尝试过通过user32实现透明效果，也改用WPF操作，均无效果。需要实现能在第三方父应用中正常显示的透明子窗口。

核心问题是分层窗口（WS_EX_LAYERED）与子窗口（WS_CHILD）的兼容性限制，Windows默认不允许同时拥有这两个属性的窗口正常渲染，可通过以下步骤解决：

• 调整属性设置顺序：先配置分层透明属性，再绑定父窗口并设置子窗口样式，避免属性冲突
• 启用WPF原生透明支持：设置窗口AllowsTransparency=true、WindowStyle=None，配合Win32 API实现分层透明
• 强制窗口重绘：设置完所有属性后触发重绘，确保透明效果生效

using System;
using System.Diagnostics;
using System.Linq;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Interop;
using System.Windows.Media;

namespace Demo
{
    public partial class MainWindow : Window
    {
        [DllImport("user32.dll", EntryPoint = "SetWindowLong")]
        private static extern int SetWindowLong32(IntPtr hWnd, int nIndex, int dwNewLong);

        [DllImport("user32.dll", EntryPoint = "SetWindowLongPtr")]
        private static extern IntPtr SetWindowLongPtr64(IntPtr hWnd, int nIndex, int dwNewLong);

        [DllImport("user32.dll")]
        public static extern int GetWindowLong(IntPtr hWnd, int nIndex);

        [DllImport("user32.dll", SetLastError = true)]
        private static extern IntPtr SetParent(IntPtr hWndChild, IntPtr hWndNewParent);

        [DllImport("user32.dll")]
        private static extern bool SetLayeredWindowAttributes(IntPtr hwnd, uint crKey, byte bAlpha, uint dwFlags);

        [DllImport("user32.dll")]
        private static extern bool RedrawWindow(IntPtr hWnd, IntPtr lprcUpdate, IntPtr hrgnUpdate, uint flags);

        public const int GWL_EXSTYLE = -20;
        public const int WS_EX_LAYERED = 0x80000;
        public const int LWA_ALPHA = 0x2;
        public const int LWA_COLORKEY = 0x1;

        public static int GWL_STYLE = -16;
        public static int WS_CHILD = 0x40000000;
        private const uint RDW_INVALIDATE = 0x0001;
        private const uint RDW_UPDATENOW = 0x0100;

        public HwndSource hwnd;

        public MainWindow()
        {
            InitializeComponent();
            // 启用WPF窗口透明基础配置
            AllowsTransparency = true;
            WindowStyle = WindowStyle.None;
            Background = Brushes.Transparent;
        }

        public static IntPtr SetWindowLongPtr(IntPtr hWnd, int nIndex, int dwNewLong)
        {
            return Environment.Is64BitOperatingSystem 
                ? new IntPtr(SetWindowLong32(hWnd, nIndex, dwNewLong)) 
                : SetWindowLongPtr64(hWnd, nIndex, dwNewLong);
        }

        private void Window_ContentRendered(object sender, EventArgs e)
        {
            hwnd = PresentationSource.FromVisual(this) as HwndSource;
            if (hwnd == null) return;

            Process hostProcess = Process.GetProcessesByName("POWERPNT").FirstOrDefault();
            if (hostProcess == null) return;

            IntPtr hostHandle = hostProcess.MainWindowHandle;
            IntPtr guestHandle = hwnd.Handle;

            // 1. 先设置分层透明属性
            int exStyle = GetWindowLong(guestHandle, GWL_EXSTYLE);
            SetWindowLongPtr(guestHandle, GWL_EXSTYLE, exStyle | WS_EX_LAYERED);
            // 设置半透明效果（200为透明度值，范围0-255）
            SetLayeredWindowAttributes(guestHandle, 0, 200, LWA_ALPHA);

            // 2. 绑定父窗口并设置子窗口样式
            SetParent(guestHandle, hostHandle);
            int style = GetWindowLong(guestHandle, GWL_STYLE);
            SetWindowLongPtr(guestHandle, GWL_STYLE, style | WS_CHILD);

            // 3. 强制窗口重绘，确保透明效果生效
            RedrawWindow(guestHandle, IntPtr.Zero, IntPtr.Zero, RDW_INVALIDATE | RDW_UPDATENOW);
        }
    }
}

内容的提问来源于stack exchange，提问作者Windmix