启动一个线程(WPF应用），更新页面控件时出错“ 调用线程无法访问此对象 ，因为另一个线程拥有该对象”，这个要如何修改？

 public void updateProcess(Label l)
  //.........
  pdh = new ProgressDialogHelper();
  pdh.ShowProgress(() =>
                {
                  
                    foreach (string runjob in runList)
                    {
			//后台任务执行
			l.Content ="加载中"；//修改时出错
                        decimal process = (decimal)i / (decimal)runList.LongCount();
                        Console.WriteLine("P:" + p);
                        if (process >= 1)
                        {
                            process = 1;
                        }
                        pdh.SetValue((double) process * 100);
                        pdh.SetMessage("当前进度 :" + process);

                    }
                    pdh.CloseProgressDialog();
                });

class ProgressDialogHelper{
//.....
public void ShowProgress(Action workAction)
        {
            this.Worker = new Thread(new ThreadStart(workAction));
            this.ProDialog = new ProgressDialog();

            Worker.Start();
            ProDialog.ShowDialog();
        }

 this.Dispatcher.Invoke(DispatcherPriority.Normal, new Action(() =>
                    {
                        this.lbInfo.Content = 进度值;
                    }));

this.Dispatcher.Invoke(DispatcherPriority.Normal, new Action(() =>
				{   pdh.ShowProgress(() =>
                       {
                   
                    foreach (string runjob in runList)
                    {
                    l.Content ="加载中";
//..........................................