Windows Service不断寻找文件

Question

Sorry if this is an stupid question, but I'm pretty new to Windows Services and want to make sure I understand the proper way to approach this situation.

I have a Windows Service that is meant to watch for files and if those files exist, it processes them. I was looking through an old developer's code and they used Thread.Sleep() if files didn't exist. I understand that this is bad practice and have seen it first-hand that this locks up the service.

Here's a simplified example of my logic:

private Task _processFilesTask;
private CancellationTokenSource _cancellationTokenSource;

public Start()
{
   _cancellationTokenSource = new CancellationTokenSource();
   _processFilesTask = Task.Run(() => DoWorkAsync(_cancellationTokenSource.Token))
}

public async Task DoWorkAsync(CancellationToken token)
{
   while(!token.IsCancellationRequested)
   {
      ProcessFiles();
      //await Task.Delay(10000);
   }
}

public Stop()
{
   _cancellationTokenSource.Cancel();
   _processFilesTask.Wait();
}

private void ProcessFiles()
{
  FileInfo xmlFile = new DirectoryInfo(Configs.Xml_Input_Path).GetFiles("*.xml").OrderBy(p => p.CreationTime).FirstOrDefault();
  if(xmlFile != null)
    {
      //read xml
      //write contents to db
      //move document specified in xml to another file location
      //delete xml
    }
}

My first question: Is any sort of Delay or Pause even needed? If I don't have any pause then this service will constantly look for files on a remote server. Is this something I have to worry about or is it a pretty light-weight process?

Second question: If it would be better to pause instead of constantly hitting this server, is this a better approach or what would you recommend?

public  async Task DoWorkAsync(CancellationToken token)
{
   while(!token.IsCancellationRequested)
   {
      ProcessFiles();
      await Task.Delay(TimeSpan.FromMilliseconds(10000), token).ContinueWith(_processFilesTask=> { });
   }
}

Thanks for your help!

Answer 1

You can use timer to check desired files and folder. Here is outline.

1. Add Timer in your service class (one that inherits ServiceBase class)

   private System.Timers.Timer myTimer;

2. Initialize timer in OnStart method.

    protected override void OnStart(string[] args) { // Set the Interval to 1 seconds (1000 milliseconds). myTimer = new System.Timers.Timer(1000); // Hook up the Elapsed event for the timer. myTimer.Elapsed += new ElapsedEventHandler(OnTimedEvent); myTimer.Enabled = true; } 

3. Define elapsed event handler.

    private void OnTimedEvent(object source, ElapsedEventArgs e) { //Write your file handling logic here. //Service will execute this code after every one second interval //as set in OnStart method. }