Multi-threading Report Progress Not Working

Question

I've recently started working with multi-threaded Winform applications and have run up against a problem I don't understand.

Basically, when I try to have a background worker report its progress and that progress comes from a calculation, it is always zero.

//making background worker
        BackgroundWorker myJanitor = new BackgroundWorker();
        myJanitor.WorkerSupportsCancellation = true;
        myJanitor.WorkerReportsProgress = true;
        myJanitor.DoWork += new DoWorkEventHandler(cleanContactList);
        myJanitor.ProgressChanged += new ProgressChangedEventHandler(myCleaningWorker_ProgressChanged);
        myJanitor.RunWorkerAsync();    

The 'cleanContactList' method loops through a DataGridView's rows, during which I try something like this:

int percentComplete = (myRow.Index  / contactGridView.Rows .Count ) * 100;                       
(sender as BackgroundWorker).ReportProgress(percentComplete);

Frustratingly, percentComplete will ALWAYS be zero. If I debug it I can see that there is an actual calculation occurring (e.g. [2000/10000]*100) but the result is always zero.

What am I missing here? If I replace the calculation with, say, a Random.Next(0,100) call it updates fine.

Answer 1

Try index * 100/count. I think you're dividing two ints leading to 0 then multiplying by 100.

For example, this:

        int index = 50;
        int count = 100;

        int percent = index/count * 100;
        int percent2 = index * 100/count;

        Console.WriteLine("{0} & {1}", percent, percent2);

Outputs 0 & 50.