如何停止加载了CSScript的脚本

我使用CS脚本库在WPF应用程序中运行用户定义的脚本。如果脚本无休止地运行，我如何取消它？当我的用户编写脚本时，我不能依赖脚本中检查的取消标志。

以下是显示问题的简化代码片段：

public partial class MainWindow : Window
{
    public string MessageFromScript
    {
        get { return (string)GetValue(MessageFromScriptProperty); }
        set { SetValue(MessageFromScriptProperty, value); }
    }
    public static readonly DependencyProperty MessageFromScriptProperty =
        DependencyProperty.Register("MessageFromScript", typeof(string), typeof(MainWindow), new PropertyMetadata(null));

    public MainWindow()
    {
        InitializeComponent();
        DataContext = this;
    }
    BackgroundWorker worker = null;
    private void OnStart(object sender, RoutedEventArgs e)
    {
        if(worker != null)
        {
            return;
        }
        worker = new BackgroundWorker();
        worker.DoWork += RunScript;
        worker.RunWorkerCompleted += ScriptCompleted;
        worker.WorkerSupportsCancellation = true;
        worker.RunWorkerAsync();
    }
    private void ScriptCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        if(e.Cancelled)
            MessageFromScript = "Script cancelled";
        else
            MessageFromScript = e.Result.ToString();
    }
    private void RunScript(object sender, DoWorkEventArgs e)
    {
        dynamic script = CSScript.Evaluator.LoadCode(@"using System;
                                using System.Threading;
                                 public class Script
                                 {
                                     public string Test()
                                     {
                                        {int count=0; while(true) { count++; Console.WriteLine(count.ToString()); Thread.Sleep(200); }}
                                        return ""Message from script"";
                                     }
                                 }");
        e.Result = script.Test();
    }
    private void OnStop(object sender, RoutedEventArgs e)
    {
        if(worker == null)
        {
            return;
        }
        //TODO: How do I stop the script here?
        worker = null;
    }
}