无法将“X”类型的对象强制转换为“X”

Question

I'm trying to parse a JSON file for a Windows Phone app, and my current code is:

 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(RootObject));
                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 songHistory = (station1)serializer.ReadObject(eargs.Result);
                    Button1.Content = songHistory.text;
                }
            };
        var uri = new Uri("<JSONGOESHERE>");
        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 RootObject
    {
        public station1 station1 { get; set; }
        public station2 station2 { get; set; }
        public station3 station3 { get; set; }
    }

I require the same fetching of text for "station2" and "station3" later as well, which is why I've left them in.

Currently, what happens is I am getting the following error when I run this on the line

var songHistory = (station1)serializer.ReadObject(eargs.Result);

InvalidCastException was unhandled by user code An exception of type 'System.InvalidCastException' occurred in APP.DLL but was not handled in user code Unable to cast object of type 'RootObject' to type 'station1'.

I had used the json2csharp generator to create the above so I'm not sure what's wrong.

Any help would be awesome.

Answer 1

You created a serializer for the type RootObject . So the output of ReadObject is that type. Just cast it correctly (there is no generic overload for ReadObject ):

var root = (RootObject)serializer.ReadObject(eargs.Result);
var songHistory = root.station1;

Answer 2

Are you sure the method doesn't also have to take a Type as a parameter for deserialization?

var songHistory = (station1)serializer.ReadObject(eargs.Result, typeof(station1));

Or maybe it has a generic overload that does the deserialization and returns a T directly?

var songHistory = serializer.ReadObject<station1>(eargs.Result);