C# messagebox 居中父窗体

在右边项目上点击右键->Add->class，添加MessageBoxEx类：

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

 public class MessageBoxEx
 {
     private static IWin32Window _owner;
     private static HookProc _hookProc;
     private static IntPtr _hHook;

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

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

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

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

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

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

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

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

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

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

     public static DialogResult Show(IWin32Window owner, string text, string caption, MessageBoxButtons buttons, MessageBoxIcon icon, MessageBoxDefaultButton defButton)
     {
         _owner = owner;
         Initialize();
         return MessageBox.Show(owner, text, caption, buttons, icon, defButton);
     }

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

     public delegate IntPtr HookProc(int nCode, IntPtr wParam, IntPtr lParam);

     public delegate void TimerProc(IntPtr hWnd, uint uMsg, UIntPtr nIDEvent, uint dwTime);

     public const int WH_CALLWNDPROCRET = ;

     public enum CbtHookAction : int
     {
         HCBT_MOVESIZE = ,
         HCBT_MINMAX = ,
         HCBT_QS = ,
         HCBT_CREATEWND = ,
         HCBT_DESTROYWND = ,
         HCBT_ACTIVATE = ,
         HCBT_CLICKSKIPPED = ,
         HCBT_KEYSKIPPED = ,
         HCBT_SYSCOMMAND = ,
         HCBT_SETFOCUS =
     }

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

     [DllImport("user32.dll")]
     private static extern int MoveWindow(IntPtr hWnd, int X, int Y, int nWidth, int nHeight, bool bRepaint);

     [DllImport("User32.dll")]
     public static extern UIntPtr SetTimer(IntPtr hWnd, UIntPtr nIDEvent, uint uElapse, TimerProc lpTimerFunc);

     [DllImport("User32.dll")]
     public static extern IntPtr SendMessage(IntPtr hWnd, int Msg, IntPtr wParam, IntPtr lParam);

     [DllImport("user32.dll")]
     public static extern IntPtr SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);

     [DllImport("user32.dll")]
     public static extern int UnhookWindowsHookEx(IntPtr idHook);

     [DllImport("user32.dll")]
     public static extern IntPtr CallNextHookEx(IntPtr idHook, int nCode, IntPtr wParam, IntPtr lParam);

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

     [DllImport("user32.dll")]
     public static extern int GetWindowText(IntPtr hWnd, StringBuilder text, int maxLength);

     [DllImport("user32.dll")]
     public static extern int EndDialog(IntPtr hDlg, IntPtr nResult);

     [StructLayout(LayoutKind.Sequential)]
     public struct CWPRETSTRUCT
     {
         public IntPtr lResult;
         public IntPtr lParam;
         public IntPtr wParam;
         public uint message;
         public IntPtr hwnd;
     } ;

     static MessageBoxEx()
     {
         _hookProc = new HookProc(MessageBoxHookProc);
         _hHook = IntPtr.Zero;
     }

     private static void Initialize()
     {
         if (_hHook != IntPtr.Zero)
         {
             throw new NotSupportedException("multiple calls are not supported");
         }

         if (_owner != null)
         {
             _hHook = SetWindowsHookEx(WH_CALLWNDPROCRET, _hookProc, IntPtr.Zero, AppDomain.GetCurrentThreadId());
         }
     }

     private static IntPtr MessageBoxHookProc(int nCode, IntPtr wParam, IntPtr lParam)
     {
         if (nCode < )
         {
             return CallNextHookEx(_hHook, nCode, wParam, lParam);
         }

         CWPRETSTRUCT msg = (CWPRETSTRUCT)Marshal.PtrToStructure(lParam, typeof(CWPRETSTRUCT));
         IntPtr hook = _hHook;

         if (msg.message == (int)CbtHookAction.HCBT_ACTIVATE)
         {
             try
             {
                 CenterWindow(msg.hwnd);
             }
             finally
             {
                 UnhookWindowsHookEx(_hHook);
                 _hHook = IntPtr.Zero;
             }
         }

         return CallNextHookEx(hook, nCode, wParam, lParam);
     }

     private static void CenterWindow(IntPtr hChildWnd)
     {
         Rectangle recChild = new Rectangle(, , , );
         bool success = GetWindowRect(hChildWnd, ref recChild);

         int width = recChild.Width - recChild.X;
         int height = recChild.Height - recChild.Y;

         Rectangle recParent = new Rectangle(, , , );
         success = GetWindowRect(_owner.Handle, ref recParent);

         Point ptCenter = new Point(, );
         ptCenter.X = recParent.X + ((recParent.Width - recParent.X) / );
         ptCenter.Y = recParent.Y + ((recParent.Height - recParent.Y) / );

         Point ptStart = new Point(, );
         ptStart.X = (ptCenter.X - (width / ));
         ptStart.Y = (ptCenter.Y - (height / ));

         ptStart.X = (ptStart.X < ) ?  : ptStart.X;
         ptStart.Y = (ptStart.Y < ) ?  : ptStart.Y;

         int result = MoveWindow(hChildWnd, ptStart.X, ptStart.Y, width,
                                 height, false);
     }

 }

调用办法

MessageBoxEx.Show(this, "Please fix the validation errors before saving.", "Validation Errors");