Question

an architectural question here.

I have a List (selected via a listview) that needs to be sent to a webservice and created in the database. I want to be able to update one at a time then update a progress bar, listview and local List with the returned ID without locking up the uithread (although i’ll have lock the listview/search controls etc they just need to be able to complete other task in different forms).

At the minute i’ve considered the following (new to most)

Background worker – the only problem here is that the progressChanged only returns an int so i’d find it difficult to return all the information I need.

Tasks – i’m using these at the minute when all I need to return a single object and then process that information (like getting list from local database and then populating listview and that works well). I can’t figure out how to spawn a thread that in turn does a loop and updates the UI Thread at the end of each pass.

parallel.foreach – don’t think this would be suitable with the web services element.

All the stuff i’ve tried so far, either locks the UI or gets cross thread exceptions.

I guess i’m looking for something that allows me to do this

createUsers(ref List<users> _users)
{
    foreach(user _u in _users)
    {
        //call webservice and update - it returns an ID or null
        string newID = webCreate(_u);
        if (newID != null)
        {
            ListViewItem lvi = listview1.FindText(_u.ListID);
            lvi.SubItems[5].Text = newID;
            _u.newID = newID;
        }
        else
        {
            lvi.SubItems[5].Text = "Error";
        }
        progressbar.value++
    }
}

There just seems to be so many options in .net 4.0 for threading I just can’t think which one will best serve me. Any pointers would be great.

Thanks, Pete.

Answer 1

If your create users is run in a separate thread. Have your form, have an updatestatusbar

delegate void updStatusbar(int i);
public UpdateStatusBar(int i)
{
  if (Statusbar1.InvokeRequred)
  {
    updStatusbar c = UpdateStatusBar;
    this.Invoke(c,new object[] {i});
  }
  else
    Statusbar1.value=i;
  }
}

Now you can call updatestatusbar from anywhere, thread or otherwise and it sorts itself out.