CODEWITHSUNDEEP
c#multithreadingbackgroundworker
John NoCookies
John NoCookies

Reputation: 1061

Update progressbar from a backgroundworker in WPF

I'm trying to make a progressbar advance using a BackgroundWorker. The final goal is to show the progress of a background search, but I first want to get to know the progress bar by doing a simple simulation. This is the code:

    public MainWindow()
    {
        InitializeComponent();

        worker = new BackgroundWorker(); // variable declared in the class
        worker.WorkerReportsProgress = true;
        worker.DoWork += new DoWorkEventHandler(worker_DoWork);
        worker.ProgressChanged += new ProgressChangedEventHandler(backgroundWorker1_ProgressChanged);
        worker.RunWorkerCompleted += worker_RunWorkerCompleted;
    }

    private void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        this.Title += " DONE";
    }

    private void worker_DoWork(object sender, DoWorkEventArgs e)
    {
        for(int j = 0; j <= 100; j++)
        {
            worker.ReportProgress(j);
            Title += j.ToString();
            Thread.Sleep(50);
        }
    }

    void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
    {
        searchProgressBar.Value = e.ProgressPercentage;
    }

But when I run it, it skips right to the end, without altering the progressbar in any way. When I debug it step-by-step, the last step I get to is worker.ReportProgress(j);, then control returns to the program and worker_RunWorkerCompleted is called. Why?

Upvotes: 3

Views: 9019

Answers (2)

Rohit Vats
Rohit Vats

Reputation: 81243

In case you trying to change the UI content, you should put the calls on UI Dispatcher. You can't modify UI objects from background thread. Replace your lines with these -

App.Current.Dispatcher.Invoke((Action)delegate()
        {
            Title += j.ToString();
        });

and

App.Current.Dispatcher.Invoke((Action)delegate()
        {
            Title = "Done";
        });

Upvotes: 1

thumbmunkeys
thumbmunkeys

Reputation: 20764

You forgot to run the worker:

     worker.RunWorkerAsync();

Upvotes: 1

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