Question

I have an httpWebRequest to access an XML and save it locally then read it and show it to the screen. Problem is, i have to do this for more than one “pivot item”, and the method that saves the xml is

private static void GetResponseCallback(IAsyncResult asynchronousResult)

and doesn’t support adding a new variable to it so i can dynamically name the xml (“tmp”+xmlName+”.xml”) .

So the question is: How do i push a variable in the xml name ?

public class HttpWebReqMethod
    {

        public void httpRequestMethod (string url, string xmlName)
        {     
            HttpWebRequest httpRequest = (HttpWebRequest)WebRequest.Create(url);
            httpRequest.ContentType = "text/xml";
            httpRequest.Method = "POST";

            httpRequest.BeginGetRequestStream(new AsyncCallback(GetRequestStreamCallback), httpRequest);
        }

        private static void GetRequestStreamCallback(IAsyncResult asynchronousResult)
        {
            HttpWebRequest httpRequest = (HttpWebRequest)asynchronousResult.AsyncState;

            // End the operation
            Stream postStream = httpRequest.EndGetRequestStream(asynchronousResult);


            string postData = "";

            // Convert the string into a byte array.
            byte[] byteArray = Encoding.UTF8.GetBytes(postData);

            // Write to the request stream.
            postStream.Write(byteArray, 0, postData.Length);
            postStream.Close();

            // Start the asynchronous operation to get the response
            httpRequest.BeginGetResponse(new AsyncCallback(GetResponseCallback), httpRequest);
        }

        private static void GetResponseCallback(IAsyncResult asynchronousResult)
        {
            HttpWebRequest httpRequest = (HttpWebRequest)asynchronousResult.AsyncState;

            // End the operation
            HttpWebResponse response = (HttpWebResponse)httpRequest.EndGetResponse(asynchronousResult);
            Stream streamResponse = response.GetResponseStream();
            StreamReader streamRead = new StreamReader(streamResponse);
            string responseStream = streamRead.ReadToEnd();

            using (var store = IsolatedStorageFile.GetUserStoreForApplication())
            {
                using (var istream = new IsolatedStorageFileStream(@"tmp" + xmlName + ".xml", FileMode.OpenOrCreate, store))
                {
                    using (var sw = new StreamWriter(istream))
                    {
                        sw.Write(responseStream);
                    }
                }
            }

            // Close the stream object
            streamResponse.Close();
            streamRead.Close();

            // Release the HttpWebResponse
            response.Close();
        }

Answer 1

Here are two things you could do:

1. make GetResponseCallback not static, and store the xmlName in an instance variable
2. pass a state object (anything that has a property named xmlName, and something else to identify it by) to the request, and you can get it from the AsyncState

3. change GetResponseCallback’s function to the following, and make the whole thing a callback “factory”

   private static AsyncCallback GetResponseCallback(string xmlName)
    {
       return (IAsyncResult asynchronousResult) =>{
       HttpWebRequest httpRequest = (HttpWebRequest)asynchronousResult.AsyncState;
       // End the operation
       HttpWebResponse response = (HttpWebResponse)httpRequest.EndGetResponse(asynchronousResult);
       Stream streamResponse = response.GetResponseStream();
       StreamReader streamRead = new StreamReader(streamResponse);
       string responseStream = streamRead.ReadToEnd();
   
       using (var store = IsolatedStorageFile.GetUserStoreForApplication())
       {
           using (var istream = new IsolatedStorageFileStream(@"tmp" + xmlName + ".xml", FileMode.OpenOrCreate, store))
           {
               using (var sw = new StreamWriter(istream))
               {
                   sw.Write(responseStream);
               }
           }
       }
   
       // Close the stream object
       streamResponse.Close();
       streamRead.Close();
   
       // Release the HttpWebResponse
       response.Close();
     }
   }
   

EDIT to ADD:
the usage then changes to

 httpRequest.BeginGetRequestStream(GetRequestStreamCallback(xmlName), httpRequest);