WPF center message box on window 2

Do you have a messagebox in a WPF application? Are you having a problem with the centering of the the messagebox in .net? I was as well. For some reason when ever i called a messagebox it would center the messagebox on what ever screen my mouse was on. Centering a messagebox on screen number two when the application is on screen number one is totally unacceptable. First let me start with credit where credit is due.   I found the main part of this code here Centering a Message box on the Active window in C#.  That code was for windows forms.  I have changed it slightly to work with WPF.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace WPFSetup.Util
{
    using System;
    using System.Runtime.InteropServices;
    using System.Windows;
    using System.Windows.Forms;
    using System.Windows.Interop;

    internal static class MessageBoxHelper
    {
        internal static void PrepToCenterMessageBoxOnForm(Window form)
        {
            MessageBoxCenterHelper helper = new MessageBoxCenterHelper();
            helper.Prep(form);
        }

        private class MessageBoxCenterHelper
        {
            private int messageHook;
            private IntPtr parentFormHandle;

            public void Prep(Window form)
            {
                NativeMethods.CenterMessageCallBackDelegate callBackDelegate = new NativeMethods.CenterMessageCallBackDelegate(CenterMessageCallBack);
                GCHandle.Alloc(callBackDelegate);

                parentFormHandle = new WindowInteropHelper(form).Handle;
                messageHook = NativeMethods.SetWindowsHookEx(5, callBackDelegate, new IntPtr(NativeMethods.GetWindowLong(parentFormHandle, -6)), NativeMethods.GetCurrentThreadId()).ToInt32();
            }

            private int CenterMessageCallBack(int message, int wParam, int lParam)
            {
                NativeMethods.RECT formRect;
                NativeMethods.RECT messageBoxRect;
                int xPos;
                int yPos;

                if (message == 5)
                {
                    NativeMethods.GetWindowRect(parentFormHandle, out formRect);
                    NativeMethods.GetWindowRect(new IntPtr(wParam), out messageBoxRect);

                    xPos = (int)((formRect.Left + (formRect.Right - formRect.Left) / 2) - ((messageBoxRect.Right - messageBoxRect.Left) / 2));
                    yPos = (int)((formRect.Top + (formRect.Bottom - formRect.Top) / 2) - ((messageBoxRect.Bottom - messageBoxRect.Top) / 2));

                    NativeMethods.SetWindowPos(wParam, 0, xPos, yPos, 0, 0, 0x1 | 0x4 | 0x10);
                    NativeMethods.UnhookWindowsHookEx(messageHook);
                }

                return 0;
            }
        }

        private static class NativeMethods
        {
            internal struct RECT
            {
                public int Left;
                public int Top;
                public int Right;
                public int Bottom;
            }

            internal delegate int CenterMessageCallBackDelegate(int message, int wParam, int lParam);

            [DllImport("user32.dll")]
            [return: MarshalAs(UnmanagedType.Bool)]
            internal static extern bool UnhookWindowsHookEx(int hhk);

            [DllImport("user32.dll", SetLastError = true)]
            internal static extern int GetWindowLong(IntPtr hWnd, int nIndex);

            [DllImport("kernel32.dll")]
            internal static extern int GetCurrentThreadId();

            [DllImport("user32.dll", SetLastError = true)]
            internal static extern IntPtr SetWindowsHookEx(int hook, CenterMessageCallBackDelegate callback, IntPtr hMod, int dwThreadId);

            [DllImport("user32.dll")]
            [return: MarshalAs(UnmanagedType.Bool)]
            internal static extern bool SetWindowPos(int hWnd, int hWndInsertAfter, int X, int Y, int cx, int cy, int uFlags);

            [DllImport("user32.dll")]
            [return: MarshalAs(UnmanagedType.Bool)]
            internal static extern bool GetWindowRect(IntPtr hWnd, out RECT lpRect);
        }
    }



}

I wont claim to understand all of what that code is doing but it does work. For more explanation on what its doing i suggest you check the main authors website.

Calling it

  MessageBoxHelper.PrepToCenterMessageBoxOnForm(this);
  MessageBox.Show("Hello!", "Hello!", MessageBoxButton.OKCancel, MessageBoxImage.Warning);