C#：Win32 Hooks（一）让下一个弹出子窗体自动显示在父窗体中心

/* ----------------------------------------------------------
文件名称：FormHelper.cs

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

namespace Splash.Windows.Forms
{
    /// <summary>
    /// 窗体扩展功能：
    ///     1.子窗体自动显示在父窗体中心位置
    /// </summary>
    public static class FormHelper
    {
        /// <summary>
        /// 子窗体自动显示在父窗体中心位置
        /// </summary>
        /// <param name="owner">要中心化子窗体的窗体</param>
        /// <remarks>扩展方法</remarks>
        public static void CenterChild(this IWin32Window owner)
        {
            CenterChildHelper helper = new CenterChildHelper();
            helper.Run(owner);
        }

        /// <summary>
        /// 基于Hook实现子窗体自动显示在父窗体中心位置
        /// </summary>
        private class CenterChildHelper
        {
            private const Int32 WH_CBT = 5;
            private const Int32 HCBT_ACTIVATE = 5;
            private const Int32 GWL_HINSTANCE = -6;

            private IntPtr _hhk;    // 钩子句柄
            private IntPtr _parent; // 父窗体句柄
            private GCHandle _gch;

            public void Run(IWin32Window owner)
            {
                NativeMethods.CBTProc CenterChildHookProc = new NativeMethods.CBTProc(CenterChildCallBack);

                // 分配新的GCHandle，保护对象不被垃圾回收
                _gch = GCHandle.Alloc(CenterChildHookProc);

                _parent = owner.Handle; // 父窗体句柄

                // 注意：dwThreadId为System.Threading.Thread.CurrentThread.ManagedThreadId不起作用
                _hhk = NativeMethods.SetWindowsHookEx(WH_CBT, CenterChildHookProc, IntPtr.Zero, NativeMethods.GetCurrentThreadId());
            }

            private IntPtr CenterChildCallBack(Int32 nCode, IntPtr wParam, IntPtr lParam)
            {
                if (nCode == HCBT_ACTIVATE)
                {   // 父窗体
                    NativeMethods.RECT formRect;
                    NativeMethods.GetWindowRect(_parent, out formRect);

                    // 子窗体
                    NativeMethods.RECT messageBoxRect;
                    NativeMethods.GetWindowRect(wParam, out messageBoxRect);

                    Int32 width = messageBoxRect.right - messageBoxRect.left;       // 消息窗体宽度
                    Int32 height = messageBoxRect.bottom - messageBoxRect.top;      // 消息窗体高度
                    Int32 xPos = (formRect.left + formRect.right - width) >> 1;     // 消息窗体位于父窗体中心时左上角X坐标
                    Int32 yPos = (formRect.top + formRect.bottom - height) >> 1;    // 消息窗体位于父窗体中心时左上角Y坐标

                    // 将消息窗体移到父窗体中心
                    NativeMethods.MoveWindow(wParam, xPos, yPos, width, height, false);

                    // 卸载钩子
                    NativeMethods.UnhookWindowsHookEx(_hhk);

                    // 释放已分配的GCHandle
                    _gch.Free();
                }

                // 允许操作
                return IntPtr.Zero;
            }
        }

        private static class NativeMethods
        {

补充：软件开发 , C# ,