A MessageBox can center within Form

MessageBoxCenter.cs

using System;
using System.ComponentModel;
using System.Diagnostics;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Text;
using System.Windows.Forms;

namespace AhDung.WinForm
{
    /// <summary>
    /// 能相对owner居中的消息框
    /// <para>- 对于MDI，是相对子窗体居中，如果希望相对于MDI，请指定owner参数为MDI</para>
    /// </summary>
    public static class MessageBoxCenter
    {
        /// <summary>
        /// 记录传入的owner，优先依据这个居中
        /// </summary>
        static IWin32Window _owner;

        // ReSharper disable UnusedMember.Global
        // ReSharper disable UnusedMethodReturnValue.Global

        public static DialogResult Show(string text)
        {
            Prepare(null);
            return MessageBox.Show(text);
        }

        public static DialogResult Show(string text, string caption)
        {
            Prepare(null);
            return MessageBox.Show(text, caption);
        }

        public static DialogResult Show(string text, string caption, MessageBoxButtons buttons)
        {
            Prepare(null);
            return MessageBox.Show(text, caption, buttons);
        }

        public static DialogResult Show(string text, string caption, MessageBoxButtons buttons, MessageBoxIcon icon)
        {
            Prepare(null);
            return MessageBox.Show(text, caption, buttons, icon);
        }

        public static DialogResult Show(string text, string caption, MessageBoxButtons buttons, MessageBoxIcon icon, MessageBoxDefaultButton defaultButton)
        {
            Prepare(null);
            return MessageBox.Show(text, caption, buttons, icon, defaultButton);
        }

        public static DialogResult Show(string text, string caption, MessageBoxButtons buttons, MessageBoxIcon icon, MessageBoxDefaultButton defaultButton, MessageBoxOptions options)
        {
            Prepare(null);
            return MessageBox.Show(text, caption, buttons, icon, defaultButton, options);
        }

        public static DialogResult Show(string text, string caption, MessageBoxButtons buttons, MessageBoxIcon icon, MessageBoxDefaultButton defaultButton, MessageBoxOptions options, string helpFilePath)
        {
            Prepare(null);
            return MessageBox.Show(text, caption, buttons, icon, defaultButton, options, helpFilePath);
        }

        public static DialogResult Show(string text, string caption, MessageBoxButtons buttons, MessageBoxIcon icon, MessageBoxDefaultButton defaultButton, MessageBoxOptions options, string helpFilePath, HelpNavigator navigator)
        {
            Prepare(null);
            return MessageBox.Show(text, caption, buttons, icon, defaultButton, options, helpFilePath, navigator);
        }

        public static DialogResult Show(string text, string caption, MessageBoxButtons buttons, MessageBoxIcon icon, MessageBoxDefaultButton defaultButton, MessageBoxOptions options, string helpFilePath, HelpNavigator navigator, object param)
        {
            Prepare(null);
            return MessageBox.Show(text, caption, buttons, icon, defaultButton, options, helpFilePath, navigator, param);
        }

        public static DialogResult Show(string text, string caption, MessageBoxButtons buttons, MessageBoxIcon icon, MessageBoxDefaultButton defaultButton, MessageBoxOptions options, string helpFilePath, string keyword)
        {
            Prepare(null);
            return MessageBox.Show(text, caption, buttons, icon, defaultButton, options, helpFilePath, keyword);
        }

        public static DialogResult Show(IWin32Window owner, string text)
        {
            Prepare(owner);
            return MessageBox.Show(owner, text);
        }

        public static DialogResult Show(IWin32Window owner, string text, string caption)
        {
            Prepare(owner);
            return MessageBox.Show(owner, text, caption);
        }

        public static DialogResult Show(IWin32Window owner, string text, string caption, MessageBoxButtons buttons)
        {
            Prepare(owner);
            return MessageBox.Show(owner, text, caption, buttons);
        }

        public static DialogResult Show(IWin32Window owner, string text, string caption, MessageBoxButtons buttons, MessageBoxIcon icon)
        {
            Prepare(owner);
            return MessageBox.Show(owner, text, caption, buttons, icon);
        }

        public static DialogResult Show(IWin32Window owner, string text, string caption, MessageBoxButtons buttons, MessageBoxIcon icon, MessageBoxDefaultButton defaultButton)
        {
            Prepare(owner);
            return MessageBox.Show(owner, text, caption, buttons, icon, defaultButton);
        }

        public static DialogResult Show(IWin32Window owner, string text, string caption, MessageBoxButtons buttons, MessageBoxIcon icon, MessageBoxDefaultButton defaultButton, MessageBoxOptions options)
        {
            Prepare(owner);
            return MessageBox.Show(owner, text, caption, buttons, icon, defaultButton, options);
        }

        public static DialogResult Show(IWin32Window owner, string text, string caption, MessageBoxButtons buttons, MessageBoxIcon icon, MessageBoxDefaultButton defaultButton, MessageBoxOptions options, string helpFilePath)
        {
            Prepare(owner);
            return MessageBox.Show(owner, text, caption, buttons, icon, defaultButton, options, helpFilePath);
        }

        public static DialogResult Show(IWin32Window owner, string text, string caption, MessageBoxButtons buttons, MessageBoxIcon icon, MessageBoxDefaultButton defaultButton, MessageBoxOptions options, string helpFilePath, HelpNavigator navigator)
        {
            Prepare(owner);
            return MessageBox.Show(owner, text, caption, buttons, icon, defaultButton, options, helpFilePath, navigator);
        }

        public static DialogResult Show(IWin32Window owner, string text, string caption, MessageBoxButtons buttons, MessageBoxIcon icon, MessageBoxDefaultButton defaultButton, MessageBoxOptions options, string helpFilePath, HelpNavigator navigator, object param)
        {
            Prepare(owner);
            return MessageBox.Show(owner, text, caption, buttons, icon, defaultButton, options, helpFilePath, navigator, param);
        }

        public static DialogResult Show(IWin32Window owner, string text, string caption, MessageBoxButtons buttons, MessageBoxIcon icon, MessageBoxDefaultButton defaultButton, MessageBoxOptions options, string helpFilePath, string keyword)
        {
            Prepare(owner);
            return MessageBox.Show(owner, text, caption, buttons, icon, defaultButton, options, helpFilePath, keyword);
        }

        // ReSharper restore UnusedMethodReturnValue.Global
        // ReSharper restore UnusedMember.Global

        private static void Prepare(IWin32Window owner)
        {
            if (_hook == IntPtr.Zero)
            {
                // ReSharper disable once CSharpWarnings::CS0618
                _hook = SetWindowsHookEx(5/*WH_CBT*/, _proc, IntPtr.Zero, AppDomain.GetCurrentThreadId());
                if (_hook == IntPtr.Zero)
                {
                    return;
                }
            }
            _owner = owner;
        }

        static IntPtr _hook;
        static readonly HookProcDelegate _proc = HookProc;

        /// <summary>
        /// 钩子消息处理过程
        /// </summary>
        private static IntPtr HookProc(int nCode, IntPtr wParam, IntPtr lParam)
        {
            Debug.WriteLine(wParam.ToString("X8") + "\thooking");

            if (nCode != 5/*HCBT_ACTIVATE*/)//仅处理窗体激活消息
            {
                return CallNextHookEx(_hook, nCode, wParam, lParam);
            }

            try
            {
                //确保操作的是消息框
                if (GetClassName(wParam) != "#32770" || !HasStyle(wParam, unchecked((int)0x80000000)))
                {
                    return CallNextHookEx(_hook, nCode, wParam, lParam);
                }

                //确定相对其居中的窗体，优先取传入的owner
                Form f = null;
                if (_owner != null)
                {
                    f = Control.FromHandle(_owner.Handle) as Form;
                }
                if (f == null)//不行再取消息框的owner
                {
                    var owner = GetParent(wParam);
                    if (owner == IntPtr.Zero)//再不行，取消息中记录的刚刚丢失焦点的窗体
                    {
                        owner = ((CBTACTIVATESTRUCT)Marshal.PtrToStructure(lParam, typeof(CBTACTIVATESTRUCT))).hWndActive;
                    }
                    if (owner != IntPtr.Zero)
                    {
                        f = Control.FromHandle(owner) as Form;
                        if (f != null && f.IsMdiContainer)//若窗体是MDI父窗体，取活动子窗体
                        {
                            f = f.ActiveMdiChild ?? f;
                        }
                    }
                }

                //如果最终都不能确定该窗体，则不移动
                if (f != null)
                {
                    var rcMsg = GetWindowRECT(wParam);
                    var rcOwn = GetWindowRECT(f.Handle);

                    var x = rcOwn.Left + (rcOwn.Width - rcMsg.Width) / 2;// rcPrv.Width / 2 - rcMsg.Width / 2;
                    var y = rcOwn.Top + (rcOwn.Height - rcMsg.Height) / 2;

                    MoveWindow(wParam, x, y, rcMsg.Width, rcMsg.Height, false);
                }

                return IntPtr.Zero;//无需再调CallNextHookEx，因为finally中已经卸载勾子，返回0表示不拦截消息，catch中同
            }
            catch (Exception ex)
            {
                Debug.WriteLine(ex);
                return IntPtr.Zero;
            }
            finally
            {
                if (UnhookWindowsHookEx(_hook))
                {
                    _hook = IntPtr.Zero;
                    Debug.WriteLine("hook unloaded.");
                }
                else
                {
                    Debug.WriteLine(new Win32Exception());
                }
            }
        }

        #region Win32 API
        // ReSharper disable FieldCanBeMadeReadOnly.Local
        // ReSharper disable MemberCanBePrivate.Local

        /// <summary>
        /// 检查窗口是否含有指定样式
        /// </summary>
        private static bool HasStyle(IntPtr hWnd, int style, bool isExStyle = false)
        {
            var s = unchecked((int)(long)GetWindowLong(hWnd, isExStyle ? -20 /*GWL_EXSTYLE*/ : -16 /*GWL_STYLE*/));
            return (s & style) == style;
        }

        private static IntPtr GetWindowLong(IntPtr hWnd, int nIndex)
        {
            return IntPtr.Size == 4
                ? GetWindowLong32(hWnd, nIndex)
                : GetWindowLongPtr64(hWnd, nIndex);
        }

        [DllImport("user32.dll", CharSet = CharSet.Auto, EntryPoint = "GetWindowLong")]
        private static extern IntPtr GetWindowLong32(IntPtr hWnd, int nIndex);

        [DllImport("user32.dll", CharSet = CharSet.Auto, EntryPoint = "GetWindowLongPtr")]
        private static extern IntPtr GetWindowLongPtr64(IntPtr hWnd, int nIndex);

        /// <summary>
        /// 获取窗口类名
        /// </summary>
        /// <exception cref="Win32Exception"/>
        private static string GetClassName(IntPtr hWnd)
        {
            var sb = new StringBuilder(255);
            if (GetClassName(hWnd, sb, sb.Capacity) == 0)
            {
                throw new Win32Exception();
            }
            return sb.ToString();
        }

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern int GetClassName(IntPtr hWnd, StringBuilder lpClassName, int nMaxCount);

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr GetParent(IntPtr hWnd);

        private delegate IntPtr HookProcDelegate(int nCode, IntPtr wParam, IntPtr lParam);

        [StructLayout(LayoutKind.Sequential)]
        private struct CBTACTIVATESTRUCT
        {
            public bool fMouse;
            public IntPtr hWndActive;
        }

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern bool UnhookWindowsHookEx(IntPtr hhk);

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr SetWindowsHookEx(int idHook, HookProcDelegate lpfn, IntPtr hMod, int dwThreadId);

        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        private static extern IntPtr CallNextHookEx(IntPtr hhook, int code, IntPtr wparam, IntPtr lparam);

        [DllImport("user32.dll", SetLastError = true)]
        private static extern bool MoveWindow(IntPtr hWnd, int x, int y, int width, int height, bool repaint);

        [DllImport("user32.dll", SetLastError = true)]
        private static extern bool GetWindowRect(IntPtr hWnd, ref RECT lpRect);

        /// <summary>
        /// 获取窗口屏幕区块
        /// </summary>
        /// <exception cref="Win32Exception"/>
        private static RECT GetWindowRECT(IntPtr hWnd)
        {
            RECT rect = new RECT();
            if (GetWindowRect(hWnd, ref rect))
            {
                return rect;
            }
            throw new Win32Exception();
        }

        [StructLayout(LayoutKind.Sequential)]
        private struct RECT
        {
            public int Left;
            public int Top;
            public int Right;
            public int Bottom;

            public int Width
            {
                get { return Right - Left; }
            }

            public int Height
            {
                get { return Bottom - Top; }
            }

            public static explicit operator Rectangle(RECT rect)
            {
                return new Rectangle(rect.Left, rect.Top, rect.Right - rect.Left, rect.Bottom - rect.Top);
            }

            public static explicit operator RECT(Rectangle rect)
            {
                return new RECT { Left = rect.Left, Top = rect.Top, Right = rect.Right, Bottom = rect.Bottom };
            }

            public override string ToString()
            {
                return string.Format("{0}, {1}, {2}, {3}", Left, Top, Width, Height);
            }
        }

        // ReSharper restore MemberCanBePrivate.Local
        // ReSharper restore FieldCanBeMadeReadOnly.Local
        #endregion
    }
}