NullReferenceException while parsing JSON - json

Question

I'm trying to parse a JSON file when someone clicks on a button, which replaces the button's Content with data from the JSON.
Currently I'm facing an issue where the data remains null. The code is as follows:
private void Button1_Tap(object sender, System.Windows.Input.GestureEventArgs e)
{
Button1.FontSize = 15;
Button1.Content = "Fetching...";
var client = new WebClient();
client.OpenReadCompleted +=
(s, eargs) =>
{
var serializer = new DataContractJsonSerializer(typeof(RadioRootObject));
if (eargs.Error != null)
{
if (eargs.Error.Message.Contains("NotFound"))
{
MessageBox.Show("Could not retrieve playlist", "Error", MessageBoxButton.OK);
Button1.Content = "Could not retrieve playlist";
}
else
{
MessageBox.Show("Could not retrieve playlist", "Error", MessageBoxButton.OK);
Button1.Content = "Could not retrieve playlist";
}
}
else
{
var root = (RadioRootObject)serializer.ReadObject(eargs.Result);
var songHistory = root.station3;
Button1.Content = songHistory.text;
}
};
var uri = new Uri("http://www.reignofcomputer.com/tmpsend/nowplaying.json");
client.OpenReadAsync(uri);
}
public class station1
{
public string station { get; set; }
public string title { get; set; }
public string artist { get; set; }
public string text { get; set; }
}
public class station2
{
public string station { get; set; }
public int listeners { get; set; }
public string title { get; set; }
public string artist { get; set; }
public string text { get; set; }
}
public class station3
{
public string station { get; set; }
public int listeners { get; set; }
public string title { get; set; }
public string artist { get; set; }
public string text { get; set; }
}
public class RadioRootObject
{
public station1 station1 { get; set; }
public station2 station2 { get; set; }
public station3 station3 { get; set; }
}
root and songHistory remain null and thus throws a NullReferenceException.
station1 and station2 are used in Button2_Tap and Button3_Tap, not shown in the above code, which are similar to Button1_Tap above.
I'm told that the DataContractJsonSerializer cannot match property "1" from the json object to the property station1 on the RadioRootObject class, but I'm not sure how go about making it match.
I am unable to alter the data in the JSON itself. Any ideas?

Answer 1

Check this blog post for how to Parsing JSON in a Windows Phone Application
And accordingly, try this
private void Button_Click(object sender, RoutedEventArgs e)
{
Button1.FontSize = 15;
Button1.Content = "Fetching...";var client = new WebClient();
var uri = new Uri("http://www.reignofcomputer.com/tmpsend/nowplaying.json");
client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(client_DownloadStringCompleted);
client.DownloadStringAsync(uri);
}
void client_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
var jobj = JObject.Parse(e.Result);
var station3 = jobj["3"];
Button1.Content = station3["text"];
}

Answer 2

Since the property in the JSON is "1" and the name of the member of RadioRootObject is "station1", these don't match. You can tell the serializer what the name in JSON is by using a DataMemberAttribute, something like
public class RadioRootObject
{
[DataMember(Name="1")]
public station1 station1 { get; set; }
[DataMember(Name="2")]
public station2 station2 { get; set; }
[DataMember(Name="3")]
public station3 station3 { get; set; }
}
Honestly, I thought you had to have [DataContract] and [DataMember] attributes on your class and members anyway (see the example for DataContractJsonSerializer), but I could be wrong :-)