Références circulaires empêchant la sérialisation du graphe d'objet

Question

J'ai un modèle de données simple impliquant les mauvaises herbes et les familles de mauvaises herbes.

WeedFamily <-1---*-> Weed (WeedFamily et Weed ont une relation un-à-plusieurs)

J'essaie de terminer mon premier ApiController afin de pouvoir facilement récupérer mes données en JSON pour une application AngularJS. Lorsque j'accède au /WeedAPI/ URL dans mon application, j'obtiens l'erreur suivante. Je suis sûr que le problème est que j'ai des références circulaires entre Weed et WeedFamily.

Comment dois-je changer mon modèle de données pour que la sérialisation JSON fonctionne tout en conservant la qualité bidirectionnelle de la relation Weed-WeedFamily?

(c'est-à-dire que je veux toujours pouvoir créer des expressions comme celle-ci:

 WeedData.GetFamilies()["mustard"].Weeds.Count

et

WeedData.GetWeeds()[3].Family.Weeds

)

L'erreur:

<Error>
    <Message>An error has occurred.</Message>
    <ExceptionMessage>
        The 'ObjectContent`1' type failed to serialize the response body for content type 'application/xml; charset=utf-8'.
    </ExceptionMessage>
    <ExceptionType>System.InvalidOperationException</ExceptionType>
    <StackTrace/>
    <InnerException>
        <Message>An error has occurred.</Message>
        <ExceptionMessage>
            Object graph for type 'WeedCards.Models.WeedFamily' contains cycles and cannot be serialized if reference tracking is disabled.
        </ExceptionMessage>
        <ExceptionType>
            System.Runtime.Serialization.SerializationException
        </ExceptionType>
        <StackTrace>
            at System.Runtime.Serialization.XmlObjectSerializerWriteContext.OnHandleReference(XmlWriterDelegator xmlWriter, Object obj, Boolean canContainCyclicReference) at WriteWeedToXml(XmlWriterDelegator , Object , XmlObjectSerializerWriteContext , ClassDataContract ) at System.Runtime.Serialization.ClassDataContract.WriteXmlValue(XmlWriterDelegator xmlWriter, Object obj, XmlObjectSerializerWriteContext context) at System.Runtime.Serialization.XmlObjectSerializerWriteContext.WriteDataContractValue(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle declaredTypeHandle) at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeWithoutXsiType(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle declaredTypeHandle) at System.Runtime.Serialization.XmlObjectSerializerWriteContext.InternalSerialize(XmlWriterDelegator xmlWriter, Object obj, Boolean isDecl...etc
        </StackTrace>
    </InnerException>
</Error>

Mes données:

public class WeedData
{
    public static Dictionary<string,WeedFamily> GetFamilies(){
        return new Dictionary<string,WeedFamily>
        {
             {"mustard",new WeedFamily("Mustard","Brassicaceae")}
            ,{"pigweed",new WeedFamily("Pigweed","Amaranthus")}
            ,{"sunflower",new WeedFamily("Sunflower","Asteraceae")}
        };
    }

    public static List<Weed> GetWeeds(){
        var Families = GetFamilies();
        return new List<Weed>
        {
             new Weed("Hairy Bittercress","Cardamine hirsuta",Families["mustard"])
            ,new Weed("Little Bittercress","Cardamine oligosperma",Families["mustard"])
            ,new Weed("Shepherd's-Purse","Capsella bursa-pastoris",Families["mustard"])
            ,new Weed("Wild Mustard","Sinapis arvensis / Brassica kaber",Families["mustard"])
            ,new Weed("Wild Radish","Raphanus raphanistrum",Families["mustard"])
            ,new Weed("Radish","Raphanus sativus",Families["mustard"])
            ,new Weed("Redroot Pigweed","Amaranthus retroflexus",Families["pigweed"])
            ,new Weed("Prickly Lettuce","Lactuca serriola",Families["sunflower"])
            ,new Weed("Spiny Sowthistle","Sonchus asper",Families["sunflower"])
            ,new Weed("Annual Sowthistle","Sonchus oleraceus",Families["sunflower"])

        };
    }
}

Mes cours de mannequin:

[Serializable]
public class Weed
{
    public string CommonName;
    public string LatinName;
    public List<WeedPhoto> Photos;
    public WeedFamily Family;

    public Weed(string commonName, string latinName)
    {
        CommonName = commonName;
        LatinName = latinName;
    }

    public Weed(string commonName, string latinName, WeedFamily family)
    {
        CommonName = commonName;
        LatinName = latinName;
        Family = family;
        Family.Weeds.Add(this);
    }

    override public string ToString()
    {
        return CommonName + " (" + LatinName + ")";
    }
}

et

[Serializable]
public class WeedFamily
{
    public string CommonName;
    public string LatinName;
    public List<Weed> Weeds;

    public WeedFamily(string commonName, string latinName)
    {
        CommonName = commonName;
        LatinName = latinName;
        Weeds = new List<Weed>();
    }
}

Enfin, l'ApiController:

public class WeedAPIController : ApiController
{
    //
    // GET: /WeedAPI/

    public IEnumerable<Weed> GetAllWeeds()
    {
        return WeedData.GetWeeds();
    }

}

Answer 1

Ajoutez [DataContract(IsReference = true)] aux objets qui ont des références circulaires.

[Serializable]
[DataContract(IsReference = true)]
public class WeedFamily

[Serializable]
[DataContract(IsReference = true)]
public class Weed

Voir http://msdn.Microsoft.com/en-us/library/vstudio/hh241056 (v = vs.100) .aspx