WP7 NullReferenceException反序列化JSON数组

Question

I've been having trouble pulling JSON data from the web into my app. I'm trying to pull a name and image from the "featuredReleases" array. Here part of the JSON:

      "featuredReleases":[
     {
        "id":860118,
        "type":"release",
        "name":"Back In Time",
        "slug":"back-in-time",
        "releaseDate":"2012-01-30",
        "publishDate":"2012-01-30",
        "exclusive":true,
        "category":"Release",
        "description":"Toolroom Records breaks new ground once again courtesy of the legendary drum and bass double act Liquid Kaos who have teamed up with vocalist Kirsty Hawkshaw for Back In Time, a drum and bass master class that will be taking over the airwaves and the clubs. Liquid Kaos need little introduction as owners of the legendary Breakbeat Kaos imprint and an impressive list of accolades between them that includes multiple UK Top 10 singles, a Mobo award and the support of the scenes most influential players Zane Lowe, Fabio & Grooverider, Mistajam and more. The most distinctive voice in dance music and a number 1 selling artist in her own right, Kirsty Hawkshaw completes this dream collaboration. Back In Time hooks you in with the haunting vocals of Kirsty Hawkshaw swirling above searing synths and atmospheric strings before dropping into organic grooves and a delectably warm bass. On the remix tip, Swedish star John Dahlb\u00e4ck provides a four to the floor electro workout, dubsteps rising star Cookie Monsta throws in a big, bass heavy re-rub whilst Toolrooms new wonder kid CaPa and Germanys deep house duo Kruse & N\u00fcrnberg complete a versatile package.",
        "currentStatus":"New Release",
        "catalogNumber":"TOOL12902Z",
        "purchasable":true,
        "images":{
           "small":{
              "width":30,
              "height":30,
              "url":"http:\/\/geo-media.beatport.com\/items\/imageCatalog\/4000000\/900000\/0\/9000\/500\/70\/4909578.jpg",
              "secureUrl":"https:\/\/media.beatport.com\/items\/imageCatalog\/4000000\/900000\/0\/9000\/500\/70\/4909578.jpg"
           },
           "medium":{
              "width":60,
              "height":60,
              "url":"http:\/\/geo-media.beatport.com\/items\/imageCatalog\/4000000\/900000\/0\/9000\/500\/70\/4909579.jpg",
              "secureUrl":"https:\/\/media.beatport.com\/items\/imageCatalog\/4000000\/900000\/0\/9000\/500\/70\/4909579.jpg"
           },
           "large":{
              "width":500,
              "height":500,
              "url":"http:\/\/geo-media.beatport.com\/items\/imageCatalog\/4000000\/900000\/0\/9000\/500\/80\/4909580.jpg",
              "secureUrl":"https:\/\/media.beatport.com\/items\/imageCatalog\/4000000\/900000\/0\/9000\/500\/80\/4909580.jpg"
           }
        }
     },

If you need to see the full JSON (its really long) here is the api to plug into a JSON Formatter . http://api.beatport.com/catalog/3/beatport/home

Here are my classes.

namespace Beatport.Classes
{
    public class NewReleasesCharts //Root Object
    {
        public Metadata metadata { get; set; }
        public ResultHome results = new ResultHome();
    public IEnumerator<ResultHome> GetEnumerator()
    {
        return this.results.GetEnumerator();
    }
}

public class ResultHome
{
    public List<FeaturedReleases> featuredReleases { get; set; }

    //public List<FeaturedCharts> featuredCharts { get; set; }
    //public List<TopDownloads> topdownloads { get; set; }
    //public List<MostPopularReleases> mostPopularReleases { get; set; }
    //public List<Components> components { get; set; }

    internal IEnumerator<ResultHome> GetEnumerator()
    {
        throw new NotImplementedException();
    }
}

public class FeaturedReleases
{
    public int id { get; set; }
    public string type { get; set; }
    public string name { get; set; }
    public string slug { get; set; }
    public ReleaseImage releaseImage { get; set; } 
}

public class ReleaseImage
{
    public ReleaseSmall releaseSmall { get; set; }
    public ReleaseMedium releaseMedium { get; set; }
    public ReleaseLarge releaseLarge { get; set; }
}

public class ReleaseMedium
{
    public int width { get; set; }
    public int height { get; set; }
    public string url { get; set; }
    public string secureUrl { get; set; }
}  

Finally, here is my handler to deserialize the JSON (with json.net) and pull out the data.

UPDATED

    // Deserialize home page data
    void jsonHome_GetDataCompleted(object snder, DownloadStringCompletedEventArgs e)
    {
        try
        {
            NewReleasesCharts homeData = JsonConvert.DeserializeObject<NewReleasesCharts>(e.Result);

            foreach (FeaturedReleases release in homeData.results.featuredReleases)
            {
                string releaseName = release.name;
                string img = release.releaseImage.releaseMedium.url;
                listGenres.Items.Add(releaseName);
                listGenres.Items.Add(img);
            }

        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }

    }

I am now getting a json.net exception when trying to deserialize NewReleasesCharts.

Cannot deserialize JSON array (ie [1,2,3]) into type 'Beatport.Classes.ResultHome'. The deserialized type must be an array or implement a collection interface like IEnumerable, ICollection or IList. To force JSON arrays to deserialize add the JsonArrayAttribute to the type. Line 1, position 58.

Answer 1

You are very close to solution.

First, deserialize as

NewReleasesCharts homeData = JsonConvert.DeserializeObject<NewReleasesCharts>(e.Result)

Then change your class definitions as

public class FeaturedReleases
{
    public int id { get; set; }
    public string type { get; set; }
    public string name { get; set; }
    public string slug { get; set; }
    public ReleaseImage images { get; set; }
}

public class ReleaseImage
{
    public ReleaseSmall small { get; set; }
    public ReleaseMedium medium { get; set; }
    public ReleaseLarge large { get; set; }
}

and finally, your loop should be something like this

foreach (FeaturedReleases release in homeData.results.featuredReleases)
{
    string releaseName = release.name;
    string img = release.images.medium.url;
    listGenres.Items.Add(releaseName);
    listGenres.Items.Add(img);
}