Position a Windows Forms MessageBox in C#

Introduction

There's no method in C# to position a MessageBox. But in C++, you can position a message box by finding the message box and moving it. In this tip, I'll tell you how to position a MessageBox in C#.

Using the Code

At the top of your code file, add these using namespace statements:

using System.Runtime.InteropServices;
using System.Threading;

In your Form class, add these DllImport attributes:

[DllImport("user32.dll")]
static extern IntPtr FindWindow(IntPtr classname, string title); // extern method: FindWindow

[DllImport("user32.dll")]
static extern void MoveWindow(IntPtr hwnd, int X, int Y, 
	int nWidth, int nHeight, bool rePaint); // extern method: MoveWindow

[DllImport("user32.dll")]
static extern bool GetWindowRect
	(IntPtr hwnd, out Rectangle rect); // extern method: GetWindowRect

The DllImportAttribute class is available in each .NET version.
Then, you need to find and move the MessageBox. To do that, use this code:  

void FindAndMoveMsgBox(int x, int y, bool repaint, string title)
{
    Thread thr = new Thread(() => // create a new thread
    {
        IntPtr msgBox = IntPtr.Zero;
        // while there's no MessageBox, FindWindow returns IntPtr.Zero
        while ((msgBox = FindWindow(IntPtr.Zero, title)) == IntPtr.Zero) ;
        // after the while loop, msgBox is the handle of your MessageBox
        Rectangle r = new Rectangle();
        GetWindowRect(msgBox, out r); // Gets the rectangle of the message box
        MoveWindow(msgBox /* handle of the message box */, x , y, 
           r.Width - r.X /* width of originally message box */, 
           r.Height - r.Y /* height of originally message box */, 
           repaint /* if true, the message box repaints */);
    });
    thr.Start(); // starts the thread
}

Call this method before you call MessageBox.Show. When you call MessageBox.Show, be sure the caption parameter isn't empty, because the title parameter must be equal to the caption parameter.

For example:

FindAndMoveMsgBox(0, 0, true,"Title");
MessageBox.Show("Message","Title");