Question

I’m developing a winform application and would make a request in the database and populate my combobox asynchronously but am having problem of access control because they come from another thread, here’s the code.

   this.backWorker.DoWork + = delegate
             {
                 comboBoxUsers.DataSource = repositoryUser.SelectAll();
                 comboBoxUsers.ValueMember = "UserId";
                 comboBoxUsers.DisplayMember = "Name";
             };

             backWorker.RunWorkerAsync ();

I am studying about envoke but I’m having trouble getting to implement this,
I needed to do was leave the DoWork event visible progress bar and select to do this.

Answer 1

Only query your repository on the BackgroundWorker and return the results through the ProgressChangedEvenHandler to the UI

   //Set the ComboBox Properties on the Form, not in the worker.
   comboBoxUsers.ValueMember = "UserId";
   comboBoxUsers.DisplayMember = "Name";

   BackgroundWorker = new BackgroundWorker();
   worker.DoWork += Worker_DoWork;
   worker.WorkerReportsProgress = true;
   worker.ProgressChanged += new ProgressChangedEventHandler(Worker_ProgressChanged);

   private void Worker_DoWork(object sender, DoWorkEventArgs e)
   {
        BackgrounderWorker worker = (BackgroundWorker)sender;

        //Query the database
        //Instantiate a custom-class to contain the results
        IList<Users> users = userRepository.SelectAll();
        QueryResults results = new QueryResults(users);
        worker.ReportProgress(0, results);
   }

   //Back In the UI Layer
   private void Worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
   {
       var result = (QueryResult)e.UserState;
       comboBoxUsers.DataSource = result.Users;
   }