Seattle Code Camp

srinathv — Mon, 24 Oct 2005 07:36:00 GMT

Today at Seattle Code Camp day 2 -- Peter & Brad gave the attendees a taste of Dependency Injection via ObjectBuilder (which is part our CAB deliverable), TDD & Pair Programming, Model-View-Presenter, Monad and CAB. The slides for the presentation will be posted at Peter's site. Both Peter & Brad fielded a lot of questions on all of the above topics.

One of the attendees asked about our the Offline App Block & how would he replace the out of the box ConnectionDetectionStrategy (because the default implementation relies on wininet api's used by Internet Explorer). I couldn't find the original article & code that came with below implementation (I think this is from David), it illustrates how to ping a web service to check for connectivity.

using System;
using System.Runtime.InteropServices;
using System.Xml.XPath;
using System.IO;
using System.Configuration;
using Microsoft.ApplicationBlocks.Common;
using Microsoft.ApplicationBlocks.SmartClient.Offline;
using System.Web;
using System.Net;

namespace Microsoft.Samples.OfflineSampleClient
{
/// <summary>
/// This is a simple implementation of a ConnectionDetectionStrategy.
/// It periodically pings the web server to see if is available.
/// </summary>
public class PingWebServerStrategy : IConnectionDetectionStrategy, IProvider
{
private int pollInterval;

public const int MinimumPollingIntervalInSeconds = 1;

  public PingWebServerStrategy()
  {
  }

  /// <summary>
  /// Getter property to retrieve the polling interval in seconds
  /// </summary>
  /// <value>Polling interaval in seconds</value>
  public int PollInterval { get { return pollInterval; }}

  /// <summary>
  /// Query method to cause provider to actively detect the connection state
  /// </summary>
  /// <returns>True if provider believes we are connected</returns>
  public bool IsConnected()
  {
   bool connected = true;

   try
   {
    HttpWebRequest _webRequest2 = (HttpWebRequest)WebRequest.Create( "http://localhost/OfflineSampleWebService/OfflineSampleWebService.asmx" );
    _webRequest2.Credentials = System.Net.CredentialCache.DefaultCredentials;
    using ( HttpWebResponse myHttpWebResponse=(HttpWebResponse)_webRequest2.GetResponse() )
    {
     if ( !_webRequest2.HaveResponse )
     {
      connected = false;
     }
    }
   }
   catch( Exception ex )
   {
    connected = false;
   }

return connected;
}

  /// <summary>
  /// IProvider.Initialize method implementation. Retrieves configuration information from app.config file
  /// </summary>
  /// <param name="configurationNode">XmlNode to parse for configuration information</param>
  public void Initialize(XPathNavigator configurationNode)
  {
   XPathNodeIterator iter = configurationNode.Select("pollingInterval");
   iter.MoveNext();

   pollInterval = GetCurrentPollingInterval(iter.Current.Value);
   if(pollInterval < MinimumPollingIntervalInSeconds)
   {
    throw new ConfigurationException(ProvidersResourceTable.GetString(ProvidersResourceTable.ConnectionManagerPollingIntervalMessage));
   }
  }

  private int GetCurrentPollingInterval( string pollingIntervalString )
  {
   try
   {
    return Convert.ToInt32(pollingIntervalString);
   }
   catch( FormatException e )
   {
    throw new ConfigurationException( ProvidersResourceTable.GetString( ProvidersResourceTable.PollingIntervalShouldBeNumeric ), e );
   }
  }
}
}

Srinath Vasireddy : Smart Client

Seattle Code Camp