How to work with webClient.OpenReadCompleted event handler?

Question

I'm using the following code and it works nice

private void somethingButton_Click(object sender, System.Windows.RoutedEventArgs e)
{
WebClient webClient = new WebClient();
webClient.OpenReadCompleted += webClient_OpenReadCompleted;
webClient.OpenReadAsync(new Uri(myUri));
}

void webClient_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e)
{
if(e.Error != null)
{
messageTextBlock.Text = e.Error.Message;
return;
}
using (Stream s=e.Result)
            {
                XDocument document = XDocument.Load(s);

                var q1 = from c in document.Descendants("result")
                        select new IndeedResult
                                {
                                    Title =((string)c.Element("title")).Trim(),
                                    ResultUri = ((string)c.Element("url")).Trim(),
                                    Date = ((string)c.Element("date")).Trim(),
                                };
myDataGrid.ItemsSource = q1;
}

But I want to add another WebClient, webClient2 that will do exactly the same but has different uri and different structure so I will have webClient2_OpenReadCompleted...

The problem is that finally I need to merge (or do some logic before merge) var q1 from webClient_OpenReadCompleted and var q2 from webClient2_OpenReadCompleted and then

var mergedQs = q1.Union(q2).ToList();
myDataGrid.ItemsSource = mergedQs

Is there a simple way how to do it? I don't know how to do it using those event handlers.

Alan Simes Alan Simes · Accepted Answer · 2012-09-09T17:15:24

Good question! Did it like this

    void webClient_OpenReadCompleted( object sender, OpenReadCompletedEventArgs e )
    {
        Stream stream = (Stream)e.Result;
        BinaryReader reader = new BinaryReader( stream );

        byte[] buffer = reader.ReadBytes( (int)stream.Length );
        Uri uri = (Uri)e.UserState;

        streams.Add( uri.AbsoluteUri, new MemoryStream( buffer ) );
    }

Note the usage of UserState in order to provide a unqiue key into my streams Dictionary. Works perfectly :-) This way you can work with as many files / images / binary data as you like!

See this to see just how powerful this can be....http://www.alansimes.com/warp3dsilverlighttestpage.html

How to work with webClient.OpenReadCompleted event handler?

1 Answers