C# - Code processing order - strange behaviour

Question

I have the follow button click event:

private void btnRun_Click(object sender, EventArgs e)
    {
        label1.Visible = true;

        if (SelectDatabase())
        {
            if (string.IsNullOrEmpty(txtFolderAddress.Text))
                MessageBox.Show("Please select a folder to begin the search.");
            else
            {

                if (cbRecurse.Checked == false || Directory.GetDirectories(initialDirectory).Length == 0)
                {
                    CheckSingleFolder();
                }
                else
                {
                    CheckSingleFolder();
                    directoryRecurse(initialDirectory);
                }

                                }
        }


    }

Effectively, it does a few checks and then starts some directory recursion looking for specific files. However, the very first line of code to make the label visible does not occur until after the directories have been recursed? Anybody know why this would be?

Thanks.

Answer 1

You're doing everything within the UI thread, which is a really bad idea - the UI doesn't get to update, react to events etc until you've finished.

You should use a background thread and update the UI with progress etc using Control.BeginInvoke, or perhaps use a BackgroundWorker.

Basically, there are two golden rules in WinForms (and similar with WPF/Silverlight):

• Don't do anything which can take a significant amount of time in the UI thread
• Don't touch any UI elements from any thread other than the UI thread