C＃计时器Backgroundworker用户控件

Question

I have a C# Windows Form Application that has a menu called Start Download Files and thi menu have then two instantiated user controls(submenu, tab menus). For each tab (user control) i have a download button and a timer that runs it every 5 minutes. I am using a private background worker which is created every time the control loads and runs a method to start download the files. That gives me a lot of troubles which i still can't find a solution for because: - when i enable the timer for both controls they start the download multiple times for each and i get into concurrency accessing the files or - cross thread exceptions

Does someone experienced something similar and maybe can give me a hint?

My code looks like this:

 public partial class ucGeneralInfo : UserControl
    {
      private BackgroundWorker backgroundWorker;

      private void TimerDownloadFrequency_Tick(object sender, ElapsedEventArgs e)
        {

            if (backgroundWorker.IsBusy != true)
            {
                backgroundWorker = new BackgroundWorker();
                backgroundWorker.DoWork += new DoWorkEventHandler(backgroundWorker_DoWork);
                backgroundWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backgroundWorker_RunWorkerCompleted);
                backgroundWorker.RunWorkerAsync(Branch);

            }
        }

        private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
        {
            Download_Process((string) e.Argument);
        }

        private void Download_Process(string Branch)
        {
         // copying files
         // processing files
        }
     }
}

Answer 1

For concurrent access, use lock .

 lock(fileLock)
 {
     wc.DownloadFileAsync (/*...*/);
 }

For Cross-thread exception use Invoke .

Invoke(new MethodInvoker(delegate
{
      timer.Enable = true;
}));