Problem with asynchronous webservice response

In my WP7 application i'm calling and consuming a webservice with these methods:

In my page .cs file:

    public void Page_Loaded(object sender, RoutedEventArgs e)
    {
        if (NavigationContext.QueryString["val"] == "One")
        {
            listAgences=JSON.callWSAgence("http://...");         

            InitializeComponent();
            DataContext = this;                
        }
    }

In my json class i have these methods :

    public List<Agence> callWSAgence(string url)
    {

            WebClient webClient = new WebClient();
            Uri uri = new Uri(url);
            webClient.OpenReadAsync(uri);

            webClient.OpenReadCompleted += new OpenReadCompletedEventHandler(OpenReadCompletedTestAgence);                

            return listAgences;
    }

    public void OpenReadCompletedTestAgence(object sender, OpenReadCompletedEventArgs e)
    {            
            StreamReader reader = new System.IO.StreamReader(e.Result);
            jsonResultString = reader.ReadToEnd().ToString();
            addAgencesToList();            
            reader.Close();
    }

    public void addAgencesToList()
    {                         
            jsonResultString = json.Substring(5, json.Length - 6);
            listAgences = JsonConvert.DeserializeObject<List<Agence>>(json);                    
    }

The problem is that the OpenReadCompletedTest method in the json class is not called right after

  webClient.OpenRea开发者_JS百科dCompleted += new OpenReadCompletedEventHandler(OpenReadCompletedTestAgence);

So the listAgences returned is empty.

But later OpenReadCompletedTest is called and everything works fined, but my view has already been loaded.

What can i do to have a kind of synchronous call or to reload my view after the webservice response being parsed and my list being filled.

---

The behaviour (problem) you are seeing is because the web request is made asynchronously.

If you want to have a separate object call the web server this will need to handle a callback to process the response or make appropriate changes itself.

Also:
- the code in the question doesn't show what the variable json is defined as. In Page_Loaded it looks like a custom class but in OpenReadCompletedTestAgence and addAgencesToList it looks like a string.
- the code in Page_Loaded sets the value of listAgences twice.

check out the following question for more information about making asychronous calls synchrously Faking synchronous calls in Silverlight WP7