Thread is not aborted and waits on dispatcher invoke?

Question

(WPF c# application) . I have mainwindow UI thread where I use a dispatcher invoke in many places of the code. From main thread I start another thread. I try to abort the thread immediately by clicking a cancel button. On cancel button click I use Thread.abort() to terminate the thread. But thread does not abort. I observed that dispatcher invoke is waiting and UI is not responding. I want to run the thread synchronously and not use begininvoke..?

button cancel event is in class A ,we are calling thread abort.

Threadx.abort();

when thread abort is called we are calling custom message box from the thread via delegate

custom message box calling looks like this and is in class A

            this.Dispatcher.Invoke((Action)(() =>
            {

                    QMessageBox = new QatMessageBox(this);
                    result = QMessageBox.Show(messageBoxTest, messageBoxCaption, messageBoxButton, messageBoxImage);


            }));

custom message box looks like this and is in a separate class

       public QatMessageBox(Window owner)
    {
        InitializeComponent();
        Owner = owner;
        this.DataContext = this;
    }