Question

I have a quite complex form that presents an option to run a script (our own type). Whilst it runs, I don’t want to lock the UI completely, so I would like to start it in a thread. So far so good, but to prevent the user messing with things I need to selectively disable parts of the UI. I could recursively set Enabled = false and then Enabled = true when the thread ends. But this ignores the state of the control at the time of running (ie controls which were disabled for various reasons would be incorrectly re-enabled). Short of building a tree of booleans, is there some other way to block input (such as the GlassPane type in Java)?

Answer 1

Don’t use DoEvents, it’s evil.

Use a panel and add all the controls you want to disable in it. When the panel will be disabled, all inner controls will appear to be disabled but the value of their Enabled property won’t be actually modified.

Here’s a working example:

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            // Disables UI elements using the panel
            this.SetPanelEnabledProperty(false);

            // Starts the background work
            System.Threading.ThreadPool.QueueUserWorkItem(new System.Threading.WaitCallback(this.Worker));
        }

        private void Worker(object state)
        {
            // Simulates some work
            System.Threading.Thread.Sleep(2000);

            // Now the work is done, enable the panel
            this.SetPanelEnabledProperty(true);
        }

        private void SetPanelEnabledProperty(bool isEnabled)
        {
            // InvokeRequired is used to manage the case the UI is modified
            // from another thread that the UI thread
            if (this.panel1.InvokeRequired)
            {
                this.panel1.Invoke(new MethodInvoker(() => this.SetPanelEnabledProperty(isEnabled)));
            }
            else
            {
                this.panel1.Enabled = isEnabled;
            }
        }
    }