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copied!<p>One solution is to use a generic handler and outsource the processing to the server on an asynchronous request. Here is a step by step: </p> <p><strong>First:</strong></p> <p>Create a generic handler in your <strong><em>web project</em></strong>. Add an ASHX file with the following code for your ProcessRequest (<em>simplified for brevity</em>): </p> <pre><code> public void ProcessRequest(HttpContext context) { context.Response.ContentType = "text/plain"; string xml = context.Request.Form["xml"].ToString(); string xpath = context.Request.Form["xpath"].ToString(); XmlReader reader = new XmlTextReader(new StringReader(xml)); XDocument doc = XDocument.Load(reader); var rawResult = doc.XPathEvaluate(xpath); string result = String.Empty; foreach (var r in ((IEnumerable<object>)rawResult)) { result += r.ToString(); } context.Response.Write(result); } </code></pre> <p>It should be noted that there are some namespaces you will need references to for xml processing: </p> <ol> <li><p>System.IO</p></li> <li><p>System.Xml</p></li> <li><p>System.Xml.XPath</p></li> <li><p>System.Xml.Linq</p></li> </ol> <p><strong>Second:</strong> </p> <p>You need some code that would allow you to make an asynchronous post to the generic handler. The code below is lengthy, but essentially you pass the following:</p> <ol> <li><p>The Uri of your generic handler</p></li> <li><p>A dictionary of key value pairs (assuming the xml document and the xpath)</p></li> <li><p>Callbacks for success and failure</p></li> <li><p>A reference to the dispatch timer of the UserControl so that you can access your UI (if necessary) in the callbacks.</p></li> </ol> <p>Here is some code I've placed in a utility class: </p> <pre><code>public class WebPostHelper { public static void GetPostData(Uri targetURI, Dictionary<string, string> dataDictionary, Action<string> onSuccess, Action<string> onError, Dispatcher threadDispatcher) { var postData = String.Join("&", dataDictionary.Keys.Select(k => k + "=" + dataDictionary[k]).ToArray()); WebRequest requ = HttpWebRequest.Create(targetURI); requ.Method = "POST"; requ.ContentType = "application/x-www-form-urlencoded"; var res = requ.BeginGetRequestStream(new AsyncCallback( (ar) => { Stream stream = requ.EndGetRequestStream(ar); StreamWriter writer = new StreamWriter(stream); writer.Write(postData); writer.Close(); requ.BeginGetResponse(new AsyncCallback( (ar2) => { try { WebResponse respStream = requ.EndGetResponse(ar2); Stream stream2 = respStream.GetResponseStream(); StreamReader reader2 = new StreamReader(stream2); string responseString = reader2.ReadToEnd(); int spacerIndex = responseString.IndexOf('|') - 1; string status = responseString.Substring(0, spacerIndex); string result = responseString.Substring(spacerIndex + 3); if (status == "success") { if (onSuccess != null) { threadDispatcher.BeginInvoke(() => { onSuccess(result); }); } } else { if (onError != null) { threadDispatcher.BeginInvoke(() => { onError(result); }); } } } catch (Exception ex) { string data2 = ex.ToString(); } } ), null); }), null); } } </code></pre> <p><strong>Third:</strong></p> <p>Make the call to your utility class and pass your xml and xpath: </p> <pre><code> private void testButton_Click(object sender, RoutedEventArgs e) { Dictionary<string, string> values = new Dictionary<string, string>(); values.Add("xml", "<Foo />"); values.Add("xpath", "/*"); //Uri uri = new Uri("http://eggs/spam.ashx"); Uri uri = new Uri("http://localhost:3230/xPathHandler.ashx"); WebPostHelper.GetPostData(uri, values, (result) => { MessageBox.Show("Your result " + result); }, (errMessage) => { MessageBox.Show("An error " + errMessage); }, this.Dispatcher); } </code></pre> <p>Let me reiterate that the code here is <strong><em>simplified for brevity</em></strong>. You may want to use a serializer to pass more complex types to and from your generic handler. You will need to write null guard "sanity checks" in a defensive way when you get values from the context.Request.Form collection. But the basic idea is as documented above.</p>

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