is it possible to BackgroundWorker will wait to another?

Question

foreach (string file in listToConvert)
{
    BackgroundWorker backgroundWorker = new BackgroundWorker();
    backgroundWorker.WorkerReportsProgress = true;
    backgroundWorker.DoWork += new DoWorkEventHandler(
    (s3, e3) =>
    {
        newFile = sendFilesToConvert(file);
    });

    backgroundWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(
    (s3, e3) =>
    {
        listBoxFiles.Items.Add(newFile);
    });

    backgroundWorker.RunWorkerAsync();
}

each file from the list will convert to another and i want that each BackgroundWorker will wait untill it's finish to convert and only then the next BackgroundWorker will start how can i do it ?

Why don't you want to convert all the files in one BackgroundWorker? — oxilumin, Mar 22 '12 at 15:24
Why would you want to use background workers then? Either way you can simply start your new background workers in the completed event of each previous one. — Steven Jeuris, Mar 22 '12 at 15:25
What version of .Net are you using. If you are using 4.0, you could use a single background worker and a concurrent queue. — pstrjds, Mar 22 '12 at 15:26
@oxilumin Oh, you read past the question and actually looked at the code! :) yeah, that would make a lot more sense. — Steven Jeuris, Mar 22 '12 at 15:26
Have you seen this? http://stackoverflow.com/questions/1333058/how-to-wait-correctly-until-backgroundworker-completes#answer-1333948 — ilivewithian, Mar 22 '12 at 15:28

score 2 · Answer 1 · answered Mar 22 '12 at 15:26

2

Don't create a Bgw in each run of the loop. That's not a good idea anyway.

Just run the foreach() inside one single Bgw.

You can use the progress event to Add the results to the listbox or collect them in a list and Add them all at once when you're finished.

answered Mar 22 '12 at 15:26

H H

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This is better than the ConcurrentQueue idea! – pstrjds Mar 22 '12 at 15:27

Stephen Gilboy · Answer 2 · 2012-03-22T15:38:43.300

1

You could use the TPL for this:

   Task<List<newFile>> task1 = Task<List<newFile>>.Factory.StartNew(() =>
   {
      List<newFile> newFiles = new List<newFile>();
     foreach(string file in fileList)
     {
        newFiles.Add(SendFilesToConvert(file));
     };

     return newFilesList;
   });


   foreach(newFile nFile in task1.Result)
   {
     listBoxFiles.Items.Add(nFile);
   };

edited Mar 22 '12 at 15:38

answered Mar 22 '12 at 15:29

Stephen Gilboy

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i am using .Net 3.5 which not include Task – user979033 Mar 22 '12 at 15:30

oxilumin · Answer 3 · 2012-03-22T15:50:53.197

As I understood, you want to update a UI element (listBoxFiles) in your scenario. So you can use the following code:

BackgroundWorker backgroundWorker = new BackgroundWorker();
backgroundWorker.WorkerReportsProgress = true;

var context = SynchronizationContext.Current;
var filesList = // clone your listToConvert if it's not a local variable or other threads can access it

backgroundWorker.DoWork += (s3, e3) =>
               {
                   foreach (string file in filesList)
                   {
                       var newFile = sendFilesToConvert(file);
                       context.Post(x => listBoxFiles.Items.Add(newFile), null);

                       // Report progress
                   }
               };

backgroundWorker.RunWorkerAsync();

this code posts a message (asynchronously) to your UI thread every time it needs to update your UI control, then UI thread dispatches it message and executes the code (ListBox.Items.Add(...)) in proper context.

is it possible to BackgroundWorker will wait to another?

3 Answers3