WP7 NullReferenceException Deserialisieren von JSON-Array

Question

Ich habe Probleme beim Ziehen von JSON-Daten aus dem Internet in meine App. Ich versuche, einen Namen und ein Bild aus dem Array "featuredReleases" zu ziehen. Hier ist ein Teil des 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" 
      } 
     } 
    }, 

Wenn Sie die volle JSON (es ist wirklich lang), hier zu sehen, ist die api in eine JSON Formatter zu stopfen. http://api.beatport.com/catalog/3/beatport/home

Hier sind meine Klassen.

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; } 
} 

Schließlich ist hier mein Handler die JSON (mit json.net) und ziehen Sie die Daten deserialisieren.

AKTUALISIERT

// 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); 
     } 

    } 

ich jetzt eine json.net Ausnahme bekommen, wenn NewReleasesCharts zu deserialisieren versuchen.

Cannot deserialize JSON array (i.e. [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

Sie sind in der Lösung sehr nahe.

Zuerst deserialisieren als

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

Dann Definitionen Ihrer Klasse ändern

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; } 
} 

und schließlich soll die Schleife so etwas wie diese

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); 
}