Using Castle.Facilities.Synchronize

I removed the last post as the formatting was horrible. Here again is my first demo app with the Synchronization facility. It is normally quite painful to try to make your WinForms application threadsafe. VS2005 made it much easier to see that you are doing something wrong. Your application will move along and then the debugger will break and you have a window with an InvalidOperationException in you face.

System.InvalidOperationException was unhandled

  Message="Cross-thread operation not valid: Control 'richTextBox' accessed from a thread other than the thread it was created on."

  Source="System.Windows.Forms"

  StackTrace:

       at System.Windows.Forms.Control.get_Handle()

       at System.Windows.Forms.RichTextBox.StreamIn(Stream data, Int32 flags)

       at System.Windows.Forms.RichTextBox.StreamIn(String str, Int32 flags)

       at System.Windows.Forms.RichTextBox.set_Text(String value)

       at SafelyUpdatingWinForm.MainForm.UpdateTime() in C:\SafelyUpdatingWinForm\SafelyUpdatingWinForm\MainForm.cs:line 38

       at SafelyUpdatingWinForm.MainForm.UpdateLoop() in C:\SafelyUpdatingWinForm\SafelyUpdatingWinForm\MainForm.cs:line 27

       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)

       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)

       at System.Threading.ThreadHelper.ThreadStart()

The IDE is nice enough though to point you in the direction of a solution How to: Make Thread-Safe Calls to Windows Forms Controls (MSDN). They suggest that for any component you want to change that you create delegates and try to use Control.Invoke to make the call on the appropriate thread. This gets very bloated when you have a large and complex UI. To simplify things, Craig Neuwirt created a new facility to plug into the Castle WindsorContainer. It can automatically martial the calls to the UI thread for you and a whole lot more. Roy Osherove has his own implementation that uses the DynamicProxy2.

Program.cs:

using System;
using System.Windows.Forms;
using Castle.Facilities.Synchronize;
using Castle.Windsor; 

namespace SafelyUpdatingWinForm {
    internal static class Program {
        [STAThread]
        private static void Main() {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault( false ); 

            WindsorContainer container = new WindsorContainer();
            container.AddFacility( "sync.facility", new SynchronizeFacility() );
            container.AddComponent( "mainform.form.class", typeof (MainForm) ); 

            Application.Run( container.Resolve( "mainform.form.class" ) as Form );
        }
    }
}

And then in the MainForm.cs:

using System;
using System.ComponentModel;
using System.IO;
using System.Net;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;
using System.Windows.Forms; 

namespace SafelyUpdatingWinForm {
    public partial class MainForm : Form {
        private Thread updateLoop;
        private bool loop = true;
        private const int delay = 2000; 

        public MainForm() {
            InitializeComponent();
        } 

        private void UpdateLoop() {
            while ( loop ) {
                UpdateTime();
                Thread.Sleep( delay );
            }
        } 

        protected virtual void UpdateTime() {
            string text = GetWebPage();
            Regex regex = new Regex( @"<b>\d\d:\d\d:\d\d<br>" );
            Match match = regex.Match( text );
            string time = match.Value.TrimStart( "<b>".ToCharArray() )
                                     .TrimEnd( "<br>".ToCharArray() );
            richTextBox.Text = time;
        } 

        private static string GetWebPage() {
            string url = "http://www.time.gov/timezone.cgi?Eastern/d/-5";
            HttpWebRequest webRequest = WebRequest.Create( url ) as HttpWebRequest;
            webRequest.Method = "GET";
            using (WebResponse webResponse = webRequest.GetResponse())  {
                using (StreamReader sr = new StreamReader( webResponse.GetResponseStream(), Encoding.UTF8 )) {
                    return sr.ReadToEnd();
                }
            }
        } 

        protected override void OnClosing( CancelEventArgs e ) {
            loop = false;
            while ( updateLoop.IsAlive ) { }
            base.OnClosing( e );
        } 

        protected override void OnLoad( EventArgs e ) {
            updateLoop = new Thread( new ThreadStart( UpdateLoop ) );
            updateLoop.Name = "UpdateLoop";
            updateLoop.Start();
            base.OnLoad( e );
        }
    }
}