Threads with backgroundworker, waits a long time . How can I avoid this

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am using thread with BackGroundWorker by this, the application is waiting for a long time to fetch 50000 records , it make the other operation to wait until this thread complete. how can i avoid the waiting process in while using thread.

What I have tried:

C#

private void btnExrtPDF_Click(object sender, RoutedEventArgs e)
     {
         if (DetailsOrSummary == "Details")
             isDetails = true;


         Dispatcher.BeginInvoke(DispatcherPriority.Input, new ThreadStart(() =>
         {
             try
             {
                 DetailReportFCBuySell = AlyexWCFService.DL.DLTTIn.FCBuySELL(transactionName, isDetails, Convert.ToDateTime(dateEdtStartDate.EditValue).Date, Convert.ToDateTime(dtpEditEndDate.EditValue).Date, Customerid, ProductID, branchID, NoOfRecords, PageIndex - 1, isBuy);
                 worker.RunWorkerAsync();
             }
             catch
             {

                 object obj = new object();

             }
         }

         ));
}

 private void worker_DoWork(object sender, DoWorkEventArgs e)
     {

         Dispatcher.Invoke(new Action(() => {
         System.Data.DataTable batchFCSB = new System.Data.DataTable();
         int row = 0;


         if (DetailReportFCBuySell.FirstOrDefault().TotalRecords > toFetchRecords)
         {

            // long RecordsIcrease = 10000;
             long RecordsIcrease = 1000;
             batchFCSB = DetailReportFCBuySell.ToDataTable();
             //Collection.Add(row, batchFCSB);
             row = 1;
             PageIndex++;

             for (long k = toFetchRecords; k < DetailReportFCBuySell.FirstOrDefault().TotalRecords; k = +toFetchRecords)
             {

                 new AlxServiceClient().Using(channel =>
                 {

                     ObservableCollection<dlreports.fcbuyselldetail> temp = AlyexWCFService.DL.DLTTIn.FCBuySELL(transactionName, isDetails, Convert.ToDateTime(dateEdtStartDate.EditValue).Date, Convert.ToDateTime(dtpEditEndDate.EditValue).Date, Customerid, ProductID, branchID, NoOfRecords, PageIndex - 1, isBuy);
                     DetailReportFCBuySell = DetailReportFCBuySell.Union(temp).ToObservableCollection();

                     row++;
                     PageIndex++;

                 });
                 toFetchRecords = toFetchRecords + RecordsIcrease;
             }
         }
         }), DispatcherPriority.ContextIdle);
     }

Posted 30-Aug-16 21:07pm

SwethaVijayan

Updated 31-Aug-16 3:31am

Patrice T

v3

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Richard Deeming · Answer 1 · 2016-08-31T03:31:00

Solution 1

You're using a BackgroundWorker to push the work onto a background thread. But you're then immediately calling Dispatcher.Invoke to push the work back onto the UI thread.

As a result, you're blocking the UI thread until your work completes, and keeping a background thread idle, waiting for your UI thread to finish doing the work.

You need to move as much of the work as possible into the background thread. Remove the outer Dispatcher.Invoke call in your worker_DoWork method. When you need to update the UI, use the ReportProgress method to pass the data back to the UI thread.

Assuming it's updating the DetailReportFCBuySell property that needs to happen on the UI thread, something like this should work:

C#

private void worker_DoWork(object sender, DoWorkEventArgs e)
{
    var batchFCSB = new System.Data.DataTable();
    int row = 0;

    if (DetailReportFCBuySell.FirstOrDefault().TotalRecords > toFetchRecords)
    {
        long RecordsIcrease = 1000;
        batchFCSB = DetailReportFCBuySell.ToDataTable();
        row = 1;
        PageIndex++;
        
        for (long k = toFetchRecords; k < DetailReportFCBuySell.FirstOrDefault().TotalRecords; k = +toFetchRecords)
        {
            new AlxServiceClient().Using(channel =>
            {
                var temp = AlyexWCFService.DL.DLTTIn.FCBuySELL(transactionName, isDetails, Convert.ToDateTime(dateEdtStartDate.EditValue).Date, Convert.ToDateTime(dtpEditEndDate.EditValue).Date, Customerid, ProductID, branchID, NoOfRecords, PageIndex - 1, isBuy);
                worker.ReportProgress(0, temp);
                row++;
                PageIndex++;
            });
            
            toFetchRecords = toFetchRecords + RecordsIcrease;
        }
    }
}

private void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    var temp = (ObservableCollection<dlreports.fcbuyselldetail>)e.UserState;
    DetailReportFCBuySell = DetailReportFCBuySell.Union(temp).ToObservableCollection();
}

NB: You'll need to set the worker.WorkerReportsProgress property to true, and wire up the worker_ProgressChanged method to the worker.ProgressChanged event.

Posted 31-Aug-16 3:31am

Richard Deeming

Comments

SwethaVijayan 31-Aug-16 9:54am

The calling thread cannot access this object because a different thread owns it.

this error found by avoid the dispacher

Richard Deeming 31-Aug-16 9:56am

So as I said, move just the code that accesses / updates the UI to the UI thread.

If you use the dispatcher to move the entire worker_DoWork function back to the UI thread, then you might as well not bother using a BackgroundWorker in the first place.

SwethaVijayan 31-Aug-16 10:08am

to avoid this what i should do. i need to avoid the application waing for long time. please give me a suitable answer .

Richard Deeming 31-Aug-16 10:12am

As I keep telling you, move as much code as possible onto the background thread. Only code which accesses or updates the UI should be pushed back onto the UI thread.

I have already given you a "suitable answer"; you just need to read and understand it.

SwethaVijayan 31-Aug-16 10:38am

i had remove the dispatcher as you said in my program an i done in another way.

private void btnExrtPDF_Click(object sender, RoutedEventArgs e)
{

if (DetailsOrSummary == "Details")
isDetails = true;
//FetchRecord();
// Task myFirstTask = Task.Factory.StartNew(FetchRecord);
lblStatus.Text = ("Progress: " + 0 + "%");
thread = new Thread(new ThreadStart(FetchRecord));

thread.Start();

}

private void FetchRecord()
{
try
{
if (Application.Current.Dispatcher.CheckAccess())
{
if (DetailsOrSummary == "Details")
isDetails = true;

DetailReportFCBuySell = AlyexWCFService.DL.DLTTIn.FCBuySELL(transactionName, isDetails, Convert.ToDateTime(dateEdtStartDate.EditValue).Date, Convert.ToDateTime(dtpEditEndDate.EditValue).Date, Customerid, ProductID, branchID, NoOfRecords, PageIndex - 1, isBuy);
long RecordsIcrease = 1000;
PageIndex++;

for (long k = toFetchRecords; k < DetailReportFCBuySell.FirstOrDefault().TotalRecords; k = +toFetchRecords)
{

new AlxServiceClient().Using(channel =>
{
ObservableCollection<DLReports.FCBuySellDetail> temp = AlyexWCFService.DL.DLTTIn.FCBuySELL(transactionName, isDetails, Convert.ToDateTime(dateEdtStartDate.EditValue).Date, Convert.ToDateTime(dtpEditEndDate.EditValue).Date, Customerid, ProductID, branchID, NoOfRecords, PageIndex - 1, isBuy);
DetailReportFCBuySell = DetailReportFCBuySell.Union(temp).ToObservableCollection();
PageIndex++;
});
toFetchRecords = toFetchRecords + RecordsIcrease;
}

ResultsData = DetailReportFCBuySell.ToDataTable();// (Collection.Where(i => i.Key == k).FirstOrDefault().Value);
ExportToOxml(true);
}
else
{
//Other wise re-invoke the method with UI thread access
Application.Current.Dispatcher.Invoke(new System.Action(() => FetchRecord()));
}
}
catch (Exception ex)
{
throw ex;
}
}

in this way also am getting the same error means the application waiting for a 30 sec

Richard Deeming 31-Aug-16 10:46am

No! You are still pushing all of the work back on to the UI thread.

You start a new background thread to execute the FetchRecord method. That method then calls CheckAccess, which returns false since you're on a background thread. The method then calls Invoke to call the method on the UI thread.

Once again, you are blocking the UI thread until your method completes, and you are keeping a background thread idle waiting for the UI thread to finish executing your method.

You need the time-consuming work to run on the background thread. It should only call back into the UI thread when it needs to access or update the UI.

If you're going to keep pushing everything back onto the UI thread, then you might as well not bother using a background thread at all.

What you're doing is essentially the same as hiring an assistant to help you get more work done. But every time you give your assistant a job, he asks you to do it for him, and sits and waits until you've finished. When you've finished doing his job, you hand him the results, and he then hands them back to you and says "job done". You don't manage to get any more work done, and your assistant (the background thread) is entirely useless.

SwethaVijayan 31-Aug-16 11:14am

ok i understood the problem but , how can i do it, can u please help me .

Richard Deeming 31-Aug-16 11:21am

Once again: do the work on the background thread, and only call Invoke when you need to access or update the UI.

Start out with no calls to Invoke. When you get the "calling thread" exception, look at the call-stack to see what you're trying to access. Move that specific bit of your code into an Invoke call, and try again. Repeat until the code works without the exception.

And remember, using a background thread is not going to speed-up your code; it's just going to keep the UI responsive whilst your code is running.

SwethaVijayan 31-Aug-16 11:25am

can u provide one example with me.

Richard Deeming 31-Aug-16 11:47am

If you're using the BackgroundWorker, and you only need to update the UI, then ReportProgress will do the job - as I posted in my answer.

For anything else, use Dispatcher.Invoke to execute the specific piece of code on the UI thread.