Question

Recently decided to write a “quick” windows form app to tag my MP3 files. Not done anything with parallelism since .Net 3.0, so I’m looking at the Parallel.ForEach method to deal with the UI locking I get when I’m using a standard foreach statement. Here’s an excerpt:

var i = 1;
var files = new List<string>(); // File list is populated using recursive method.

foreach(var f in files) {
    // Add a row
    var row = dgvList.Rows[dgvList.Rows.Add()];

    // Update label
    lblSummary.Text = string.Concat("Processing... ", i);
    // Do things with row

    // Increment progress bar
    progressBar.PerformStep();
    i++;
}

I’ve figured out the simple usage of Parallel.ForEach(), but I’m not sure I should be using that particular method to update the UI? Any suggestions?

Answer 1

OK, I found the best way to achieve this is by running something like this:

// Kick off thread
Task.Factory.StartNew(delegate{
     foreach(var x in files) {
         // Do stuff

         // Update calling thread's UI
         Invoke((Action)(() => {
              progressBar.PerformStep();
         }));
     }
}

I actually updated my code to populate a List within the foreach loop, then assign that to the daragrid via .DataSource, instead of working with the .Rows collection directly. Should have done that from the start really 🙂