循环引用$对象图的对$ pventing系列化 [英] Circular references preventing serialization of object graph

问题描述

我有涉及杂草及其家庭提供简单的数据模型。

WeedFamily＆LT; -1 --- * - ＆GT;杂草（WeedFamily和杂草有一到一对多的关系）

我试图完成我的第一个ApiController，这样我可以轻松地检索我的数据作为JSON用于AngularJS应用。当我在应用程序访问 / WeedAPI / URL，我得到以下错误。我是pretty确定问题是，我有之间循环引用杂草和 WeedFamily 。

我应该如何改变我的数据模型，使同时保持双向品质JSON序列化将工作杂草 - WeedFamily 关系？

（即我希望仍然能够建立前pressions这样的：

  WeedData.GetFamilies（）[芥末。Weeds.Count
 

和

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

）

错误：

 ＆LT;错误＆GT;
    ＆LT;消息方式＆gt;发生错误＆LT; /信息＆GT;
    ＆LT; ExceptionMessage＆GT;
        在'ObjectContent`1类型没有序列化响应正文内容类型application / xml进行;字符集= UTF-8。
    ＆LT; / ExceptionMessage＆GT;
    ＆LT; ExceptionType＆GT; System.InvalidOperationException＆LT; / ExceptionType＆GT;
    ＆LT;堆栈跟踪/＆GT;
    ＆LT;＆的InnerException GT;
        ＆LT;消息方式＆gt;发生错误＆LT; /信息＆GT;
        ＆LT; ExceptionMessage＆GT;
            类型对象图WeedCards.Models.WeedFamily'包含周期，如果参考禁止追踪无法被序列化。
        ＆LT; / ExceptionMessage＆GT;
        ＆LT; ExceptionType＆GT;
            System.Runtime.Serialization.SerializationException
        ＆LT; / ExceptionType＆GT;
        ＆LT;＆栈跟踪GT;
            在System.Runtime.Serialization.XmlObjectSerializerWriteContext.OnHandleReference（XmlWriterDelegator的XmlWriter，obj对象，布尔canContainCyclicReference）在WriteWeedToXml（XmlWriterDelegator，对象，XmlObjectSerializerWriteContext，ClassDataContract）在System.Runtime.Serialization.ClassDataContract.WriteXmlValue（XmlWriterDelegator的XmlWriter，obj对象，XmlObjectSerializerWriteContext背景）在System.Runtime.Serialization.XmlObjectSerializerWriteContext.WriteDataContractValue（DataContract dataContract，XmlWriterDelegator的XmlWriter，obj对象，的RuntimeTypeHandle declaredTypeHandle）在System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeWithoutXsiType（DataContract dataContract，XmlWriterDelegator的XmlWriter，obj对象，的RuntimeTypeHandle declaredTypeHandle）的系统。 Runtime.Serialization.XmlObjectSerializerWriteContext.InternalSerialize（XmlWriterDelegator的XmlWriter，obj对象，布尔isDecl ...等
        ＆LT; /堆栈跟踪＆GT;
    ＆LT; /＆的InnerException GT;
＆LT; /错误＆GT;
 

我的数据：

 公共类WeedData
{
    公共静态字典＆LT;字符串，WeedFamily＆GT; GetFamilies（）{
        返回新字典＆LT;字符串，WeedFamily＆GT;
        {
             {芥末，新WeedFamily（芥末，十字花科）}
            ，{藜，新WeedFamily（藜，苋）}
            {向日葵，新WeedFamily（向日葵，菊科）}
        };
    }    公共静态列表＆LT;杂草＆GT; GetWeeds（）{
        VAR家庭= GetFamilies（）;
        返回新的List＆LT;杂草＆GT;
        {
             新的杂草（毛Bittercress，碎米荠，家庭[芥末]）
            ，新的杂草（小Bittercress，碎米oligosperma家庭[芥末]）
            ，新的杂草（荠菜，荠菜，家庭[芥末]）
            ，新的杂草（野芥菜，野芥/田芥，家庭[芥末]）
            ，新的杂草（野萝卜，野萝卜，家庭[芥末]）
            ，新的杂草（萝卜，萝卜，家庭[芥末]）
            ，新的杂草（反枝苋，反枝苋，家庭[猪草]）
            ，新的杂草（野莴苣，野莴苣，家庭[向日葵]）
            ，新的杂草（刺苦菜，花叶滇苦菜，家庭[向日葵]）
            ，新的杂草（「股东周年苦菜，荼，家庭[向日葵]）        };
    }
}
 

我的模型类：

  [Serializable接口]
公共类杂草
{
    公共字符串通用名称;
    公共字符串LatinName;
    公开名单＆LT; WeedPhoto＆GT;相片;
    公共WeedFamily家庭;    公共杂草（字符串COMMONNAME，串latinName）
    {
        通用名称=通用名称;
        LatinName = latinName;
    }    公共杂草（字符串COMMONNAME，串latinName，WeedFamily家族）
    {
        通用名称=通用名称;
        LatinName = latinName;
        家庭=家庭;
        Family.Weeds.Add（本）;
    }    覆盖公共字符串的ToString（）
    {
        返回通用名称+（+ LatinName +）;
    }
}
 

和

  [Serializable接口]
公共类WeedFamily
{
    公共字符串通用名称;
    公共字符串LatinName;
    公开名单＆LT;杂草＆GT;杂草;    公共WeedFamily（字符串COMMONNAME，串latinName）
    {
        通用名称=通用名称;
        LatinName = latinName;
        杂草=新的List＆LT;杂草＆GT;（）;
    }
}
 

最后，ApiController：

 公共类WeedAPIController：ApiController
{
    //
    // GET：/ WeedAPI /    公共IEnumerable的＆LT;杂草＆GT; GetAllWeeds（）
    {
        返回WeedData.GetWeeds（）;
    }}
 

解决方案

添加 [DataContract（IsReference = TRUE）] 来有循环引用的对象。

  [Serializable接口]
[DataContract（IsReference =真）]
公共类WeedFamily[Serializable接口]
[DataContract（IsReference =真）]
公共类杂草
 

请参阅http://msdn.microsoft.com/en-us/library/vstudio/hh241056(v=vs.100).aspx

I've got a simple data model involving Weeds and Weed Families.

WeedFamily <-1---*-> Weed (WeedFamily and Weed have a one-to-many relationship)

I'm attempting to complete my first ApiController so that I can easily retrieve my data as JSON for an AngularJS application. When I access the /WeedAPI/ URL in my application, I get the following error. I'm pretty sure the problem is that I have circular references between Weed and WeedFamily.

How should I change my data model so that the JSON serialization will work while maintaining the bi-directional quality of the Weed-WeedFamily relationship?

(ie. I want to still be able to build expressions like the following:

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

and

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

)

The error:

<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>

My data:

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"])

        };
    }
}

My model classes:

[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 + ")";
    }
}

and

[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>();
    }
}

Finally, the ApiController:

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

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

}

解决方案

Add [DataContract(IsReference = true)] to the objects that have circular references.

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

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

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

这篇关于循环引用$对象图的对$ pventing系列化的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！