Don't show dropdown in Autocompletebox in windows phone - windows-phone-7

Question

I get response from server, it is Json where are data about street names. Then I parse response string to Json, and add street names to list. I want that this list show like dropdown in Autocompletebox, when text length equals two(I press second character in Autocompletebox).
Also I use Json.Net library.
I use this code:
Here is class(JsonWorker) I use:
class JsonWorker
{
public async Task<HttpWebResponse> send(string requestUrl, JObject jsonObjesct)
{
HttpWebRequest request = (HttpWebRequest) WebRequest.Create(requestUrl);
request.ContentType = "text/plain; charset=utf-8";
request.Method = "POST";
byte[] jsonAsBytes = Encoding.UTF8.GetBytes(jsonObjesct.ToString());
Stream x = await request.GetRequestStreamAsync();
await x.WriteAsync(jsonAsBytes, 0, jsonAsBytes.Length);
x.Close();
HttpWebResponse response = (HttpWebResponse) (await request.GetResponseAsync());
return response;
}
public async Task<string> get(
HttpWebResponse response)
{
var stream = response.GetResponseStream();
var sr = new StreamReader(stream);
string str_responsefromjson = await sr.ReadToEndAsync();
sr.Close();
stream.Close();
return str_responsefromjson;
}
Here is method(GetSteets):
private async Task<List<string>> GetStreets()
{
JObject jo = new JObject();
jo.Add("chars", AutoCompleteBox_Streets.Text);
jo.Add("city_id", "1");
JsonWorker jWorker = new JsonWorker();
var response = await jWorker.send("website", jo);
string str_responseformjson = await jWorker.get(response);
jo = JObject.Parse(str_responseformjson);
JArray ja = (JArray)jo["street"];
List<string> list_Streets = new List<string>();
foreach (var elem in ja)
{
list_Streets.Add(elem["title"].ToString());
}
return list_Streets;
}
Here is when I call the method above:
private async void AutoCompleteBox_Streets_TextChanged(object sender, RoutedEventArgs e)
{
if (AutoCompleteBox_Streets.Text.Length.Equals(2))
{
AutoCompleteBox_Streets.ItemsSource = await GetStreets();
//On the string of code above in debug, ItemSource contains list of streets
}
}
And when I enter the second character in Autocompletebox, it don't show dropdownlist. Please help.

Answer 1

Edit
After understanding your use case then what you need is use the Populating event. This event is fired when you want to populate the drop-down with possible matches. To make this called once 2 characters or more have been typed you will also need to set MinimumPrefixLength to 2.
Moreover, change your GetStreets method to take a string param containing the chars in the textbox.
// Your page Loaded event. Bind this event in your xaml.
private void PhoneApplicationPage_Loaded(object sender, RoutedEventArgs e) {
AutoCompleteBox_Streets.MinimumPrefixLength = 2;
AutoCompleteBox_Streets.Populating += AutoComplete_Populating;
}
private async void AutoComplete_Populating(object sender, PopulatingEventArgs e) {
// e.Parameter will contain the chars in your textbox.
AutoCompleteBox_Streets.ItemsSource =
await GetStreets(HttpUtility.UrlEncode(e.Parameter));
AutoCompleteBox_Streets.PopulateComplete();
}
private async Task<List<string>> GetStreets(string chars) {
JObject jo = new JObject();
jo.Add("chars", chars);
// Rest of your method code
// ...
}
What you need is setting MinimumPrefixLength property to 2.
Also move your bindings to the constructor and remove the TextChanged event.
// Your constructor
public MyPage() {
InitializeComponent();
BindStreetNames();
}
private async void BindStreetNames() {
AutoCompleteBox_Streets.ItemsSource = await GetStreets();
AutoCompleteBox_Streets.MinimumPrefixLength = 2;
}
private async void AutoCompleteBox_Streets_TextChanged(object sender, RoutedEventArgs e) {
/* Remove this handler */
}