CODEWITHSUNDEEP
jsonsilverlightwindows-phone-7deserialization
Sesha S
Sesha S

Reputation: 283

Json in Windows phone 7

Hi I am using the DataContractJsonSerializer to serialize Json which is as follows

{
"meta" : {
    "code" : 200
},
"response" : {
    "venues" : [{
            "id" : "4eeb4c51775b1d4812e0261c",
            "name" : "Shake Shack",
            "contact" : {
                "phone" : "7183077590",
                "formattedPhone" : "(718) 307-7590"
            },
            "location" : {
                "address" : "409 Fulton St.",
                "crossStreet" : "at Boerum Pl.",
                "lat" : 40.692143731043416,
                "lng" : -73.98904329061085,
                "distance" : 1272,
                "postalCode" : "11201",
                "city" : "Brooklyn",
                "state" : "NY",
                "country" : "United States"
            },
            "categories" : [{
                    "id" : "4bf58dd8d48988d16c941735",
                    "name" : "Burger Joint",
                    "pluralName" : "Burger Joints",
                    "shortName" : "Burgers",
                    "icon" : {
                        "prefix" : "https:\/\/foursquare.com\/img\/categories\/food\/burger_",
                        "sizes" : [32, 44, 64, 88, 256],
                        "name" : ".png"
                    },
                    "primary" : true
                }
            ],
            "verified" : false,
            "stats" : {
                "checkinsCount" : 2812,
                "usersCount" : 1945,
                "tipCount" : 38
            },
            "url" : "http:\/\/shakeshack.com",
            "specials" : {
                "count" : 0,
                "items" : []
            },
            "hereNow" : {
                "count" : 0
            }
        }, {
            "id" : "49e644c6f964a5202f641fe3",
            "name" : "Starbucks",
            "contact" : {
                "phone" : "2122192961",
                "formattedPhone" : "(212) 219-2961",
                "twitter" : "Starbucks"
            },
            "location" : {
                "address" : "72 Spring St.",
                "crossStreet" : "at Crosby St.",
                "lat" : 40.722642,
                "lng" : -73.997989,
                "distance" : 2526,
                "postalCode" : "10012",
                "city" : "New York",
                "state" : "NY",
                "country" : "United States"
            },
            "categories" : [{
                    "id" : "4bf58dd8d48988d1e0931735",
                    "name" : "Coffee Shop",
                    "pluralName" : "Coffee Shops",
                    "shortName" : "Coffee Shop",
                    "icon" : {
                        "prefix" : "https:\/\/foursquare.com\/img\/categories\/food\/coffeeshop_",
                        "sizes" : [32, 44, 64, 88, 256],
                        "name" : ".png"
                    },
                    "primary" : true
                }
            ],
            "verified" : true,
            "stats" : {
                "checkinsCount" : 15042,
                "usersCount" : 6472,
                "tipCount" : 73
            },
            "specials" : {
                "count" : 0,
                "items" : []
            },
            "hereNow" : {
                "count" : 0
            }
            }
        ]
    }
}

My code is as follows

Stream stream = new MemoryStream(Encoding.Unicode.GetBytes(e.Result));
DataContractJsonSerializer obj = new DataContractJsonSerializer(typeof(Foursq));
Foursq result = obj.ReadObject(stream) as Foursq;

I get an ArgumentException when I try to ReadObject. If the classes I create do not match the result should be just null right? Why am I getting an ArgumentException? Is my json difficult to parse? Thanks for helping.

Edit: Below is the Stack trace.

System.ArgumentException was unhandled
Message=ArgumentException
StackTrace:
   at System.Reflection.FieldInfo.SetValue(Object obj, Object value)
   at System.Runtime.Serialization.Json.ObjectToDataContractConverter.SetMemberValue(Object newInstance, Object value, MemberInfo memInfo)
   at System.Runtime.Serialization.Json.ObjectToDataContractConverter.ReadClassDataContractMembers(DataContractJsonSerializer serializer, ClassDataContract dataContract, Dictionary`2 deserialzedValue, Object newInstance, XmlObjectSerializerReadContextComplexJson context)
   at System.Runtime.Serialization.Json.ObjectToDataContractConverter.ConvertDictionaryToClassDataContract(DataContractJsonSerializer serializer, ClassDataContract dataContract, Dictionary`2 deserialzedValue, XmlObjectSerializerReadContextComplexJson context)
   at System.Runtime.Serialization.Json.DataContractJsonSerializer.ConvertObjectToDataContract(DataContract contract, Object value, XmlObjectSerializerReadContextComplexJson context)
   at System.Runtime.Serialization.Json.ObjectToDataContractConverter.ConvertICollectionToCollectionDataContract(DataContractJsonSerializer serializer, CollectionDataContract contract, Object deserializedValue, XmlObjectSerializerReadContextComplexJson context)
   at System.Runtime.Serialization.Json.DataContractJsonSerializer.ConvertObjectToDataContract(DataContract contract, Object value, XmlObjectSerializerReadContextComplexJson context)
   at System.Runtime.Serialization.Json.ObjectToDataContractConverter.ReadClassDataContractMembers(DataContractJsonSerializer serializer, ClassDataContract dataContract, Dictionary`2 deserialzedValue, Object newInstance, XmlObjectSerializerReadContextComplexJson context)
   at System.Runtime.Serialization.Json.ObjectToDataContractConverter.ConvertDictionaryToClassDataContract(DataContractJsonSerializer serializer, ClassDataContract dataContract, Dictionary`2 deserialzedValue, XmlObjectSerializerReadContextComplexJson context)
   at System.Runtime.Serialization.Json.DataContractJsonSerializer.ConvertObjectToDataContract(DataContract contract, Object value, XmlObjectSerializerReadContextComplexJson context)
   at System.Runtime.Serialization.Json.ObjectToDataContractConverter.ReadClassDataContractMembers(DataContractJsonSerializer serializer, ClassDataContract dataContract, Dictionary`2 deserialzedValue, Object newInstance, XmlObjectSerializerReadContextComplexJson context)
   at System.Runtime.Serialization.Json.ObjectToDataContractConverter.ConvertDictionaryToClassDataContract(DataContractJsonSerializer serializer, ClassDataContract dataContract, Dictionary`2 deserialzedValue, XmlObjectSerializerReadContextComplexJson context)
   at System.Runtime.Serialization.Json.DataContractJsonSerializer.ConvertObjectToDataContract(DataContract contract, Object value, XmlObjectSerializerReadContextComplexJson context)
   at System.Runtime.Serialization.Json.DataContractJsonSerializer.ReadObject(Stream stream)
   at PanoramaApp1.MainPage.wc_DownloadStringCompleted(Object sender, DownloadStringCompletedEventArgs e)
   at System.Net.WebClient.OnDownloadStringCompleted(DownloadStringCompletedEventArgs e)
   at System.Net.WebClient.DownloadStringOperationCompleted(Object arg)
   at System.Reflection.RuntimeMethodInfo.InternalInvoke(RuntimeMethodInfo rtmi, Object obj, BindingFlags invokeAttr, Binder binder, Object parameters, CultureInfo culture, Boolean isBinderDefault, Assembly caller, Boolean verifyAccess, StackCrawlMark& stackMark)
   at System.Reflection.RuntimeMethodInfo.InternalInvoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, StackCrawlMark& stackMark)
   at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters)
   at System.Delegate.DynamicInvokeOne(Object[] args)
   at System.MulticastDelegate.DynamicInvokeImpl(Object[] args)
   at System.Delegate.DynamicInvoke(Object[] args)
   at System.Windows.Threading.DispatcherOperation.Invoke()
   at System.Windows.Threading.Dispatcher.Dispatch(DispatcherPriority priority)
   at System.Windows.Threading.Dispatcher.OnInvoke(Object context)
   at System.Windows.Hosting.CallbackCookie.Invoke(Object[] args)
   at System.Windows.Hosting.DelegateWrapper.InternalInvoke(Object[] args)
   at System.Windows.RuntimeHost.ManagedHost.InvokeDelegate(IntPtr pHandle, Int32     nParamCount, ScriptParam[] pParams, ScriptParam& pResult)

Upvotes: 1

Views: 705

Answers (1)

Codo
Codo

Reputation: 78855

According to Microsoft's documentation, an ArgumentException can occurr in FieldInfo.SetValue, if

  • The field does not exist on the object, or
  • The value parameter cannot be converted and stored in the field.

The first one is unlikely. So the second one most likely is the cause.

It means that you have a class with a property/field that is of a type incompatible with what you receive in the JSON data, e.g. the field is an integer, but you receive a string.

The stack trace further indicates that the problematic field is nested three levels deep, where the third level is a collection. If I interpret this correctly, it could e.g. be the id field of the categories.

Upvotes: 2

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