Force MessageBox to be on top of application window in .net/WPF

Use the version of MessageBox.Show that takes a Window "owner" and pass your window.

MessageBox.Show(Application.Current.MainWindow, "Im always on top - of the main window");

If your possibly not on the UI thread try:

string msg="Hello!";if (Application.Current.Dispatcher.CheckAccess()) {    MessageBox.Show(Application.Current.MainWindow, msg);}else {    Application.Current.Dispatcher.Invoke(DispatcherPriority.Normal, new Action(()=>{        MessageBox.Show(Application.Current.MainWindow, msg);    }));}

You can:
1. Invoke to block your thread until MessageBox is dismissed OR
2. BeginInvoke in which case your thread code will continue to execute but UI thread will block on MessageBox until its dismissed).

This is a quick way of putting the Message Box on top of the application windows.

MessageBox.Show(this ,"Output text"));

Inside your "public partial class MainWindow : Window" place the following code. So the Invoke will run your code inside UI thread.

void ShowErrorMessage(ERROR err){    this.Dispatcher.Invoke((Action)(() =>    {        MessageBox.Show(err.description, err.code.ToString(), MessageBoxButton.OK, MessageBoxImage.Error);    }));}