private void ConditionalGetXml(DateTime LocalDate)
{ 
    string path = "http://www.microsoft.com/china/msdn/webcast/sdk/info.xml";
    //create HttpWebRequest
    request = (HttpWebRequest)WebRequest.Create(path);
    request.IfModifiedSince = LocalDate;
    request.Method = WebRequestMethods.Http.Get;
    //try to get response
    try
    {
        response = (HttpWebResponse)request.GetResponse();
    }
    catch (Exception e) //For some reason the HttpWebResponse class throws an exception on 3xx responses
    {
        WebException we = e as WebException;
        if ( we != null && we.Response != null)
        {
            response = (HttpWebResponse)we.Response;
        }
        else
        {
            throw;
        }
    }
    //if responseCode is 304,which means no need to update.
    if (response.StatusCode == HttpStatusCode.NotModified)//check if not modified
    {
        response.Close();
        this.resultObj = "NotModified";
        return;
    }
    //if means there is something mistake.
    else if (response.ContentLength == -1)
    {
        throw new ApplicationException(StringResources.ERROR_GetInfoXML + response.StatusDescription + "(" + response.StatusCode.ToString() + ")");
    }
    else if (response.ContentType == "text/xml") //the index.zip is updated since last time
    {

        File.Delete(InfoXmlPath);

        //set message
        this.InitManager.SetMessage(StringResources.BeginDownload + DataFileName);
        //get last modified date of 
        DateTime LastModified = response.LastModified;
        //get the network stream
        Stream netStream = response.GetResponseStream();
        //create the file local stream
        try
        {
            fsStream = new FileStream(InfoXmlPath, FileMode.Create, FileAccess.ReadWrite, FileShare.None);
            //set the creation time as minValue in case the download is interrputed.

            //download
            long length = response.ContentLength;
            byte[] buffer = new byte[1024];
            fsStream.SetLength(response.ContentLength);
            int iRead = 0;
            while (fsStream.Position < length)
            {
                iRead = netStream.Read(buffer, 0, 1024);
                fsStream.Write(buffer, 0, iRead);
                //set message
                int percentage = (int)(fsStream.Position * 100 / length);
                this.InitManager.SetMessage(StringResources.Downloading + percentage.ToString() + "%");
            }
            fsStream.Close();
        }
        catch
        {
            //close the stream to set the last write time
            fsStream.Close();
            throw;
        }
        finally
        {
            netStream.Close();
        }

        File.SetLastWriteTime(InfoXmlPath, LastModified);
        //set message
        this.resultObj = "Modified";
        // Extract this zip file to l
    }
}

this.ConditionalGet(localDate);

this.ConditionalGetXml(localDate);

//檢查新版本數據
//task = new CheckNewVersionTask();
//task.InitManager = this.initalizer1;
//task.Invoke();

//工廠
public static void LoadXml()
{
    CourseXmlParser parser = new InfoXMLParser();
    parser.ParseCourseXml();
    if (OnCourseAddedFinished != null)
    {
        //OnCourseAddedFinished(parser, EventArgs.Empty);
    }
}

http://www.daiyue.info/download.aspx

http://www.microsoft.com/china/msdn/webcast/download.aspx

private void onFinished()
{
    this.cData.LifetimeStatue = LifetimePosition.DownloadProcessed;
    this.cData.RunState = RunningStatue.Finished;
    //this.RegisterForCounter();
    if (OnFileDownloaded != null)
    {
        OnFileDownloaded(this.cData);
    }
}