Unable to parse JSON array in WCF REST

Question

This is my JSON file that contains multiple objects of "Application":

{"Application":[{"appid":"0","appname":"application0"},
                {"appid":"1","appname":"application1"},
                ....
               ]}

I'm receiving it from Android code into my WCF REST service method:

[WebInvoke(Method = "POST", UriTemplate = "/AcceptApp", RequestFormat = WebMessageFormat.Json,  
    ResponseFormat = WebMessageFormat.Xml, BodyStyle = WebMessageBodyStyle.WrappedRequest)]
[OperationContract]
string AcceptApplication(Stream jsonstring);

And here's method definition:

public string AcceptApplication(Stream inputStream)
{
    StreamReader r = new StreamReader(inputStream);
    string jsonstring = r.ReadToEnd();
    try
    {
       List<ApplicationEntity> list = JsonConvert.DeserializeObject<List<ApplicationEntity>>(jsonstring);
       for (int i = 0; i < list.Count; i++)
       {
         // using data
       }
    }
    catch (Exception E)
    {
        Logger.Error(E.Message);
    }

My ApplicationEntity:

public class ApplicationEntity
{
    public string appid { get; set; }
    public string appname { get; set; }
}

I'm getting jsonstring , but error I'm getting:

Newtonsoft.Json.JsonSerializationException: Cannot deserialize the current JSON object (e.g.    
{"name":"value"}) into type  
'System.Collections.Generic.List`1[ApplicationEntity]' because the  
type requires a JSON array (e.g. [1,2,3]) to deserialize correctly.
To fix this error either change the JSON to a JSON array (e.g. [1,2,3]) or change the deserialized type so
that it is a normal .NET type (e.g. not a primitive type like integer, not a collection type like an array 
or List<T>) that can be deserialized from a JSON object. JsonObjectAttribute can also be added to the type 
to force it to deserialize from a JSON object.

Leo · Accepted Answer · 2012-07-13 07:50:02Z

2

The JSON string you are trying to parse is not a list or an array. It is an object with a property called "Application" that is an array. Try this:

public class ApplicationObject
{
    public List<ApplicationEntity> Application { get; set; }
}
...
var apps = JsonConvert.DeserializeObject<ApplicationObject>(jsonstring);

Now you can access the list on apps.Application.

edited Jul 13, 2012 at 7:50

answered Jul 13, 2012 at 3:10

Leo

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4 Comments

benjamin54 Over a year ago

It gave me error: Object reference not set to an instance of an object. foreach (var item in apps.Applications) { try { ApplicationEntity ent = new ApplicationEntity(); ent = item; Status = InsertInstalledApps(ent); } catch (Exception ex) { Logger.Error( ex); } }

Leo Over a year ago

You do not need to create a ApplicationEntity instance, the "item" on your foreach alreay is a ApplicationEntity instance. So you just need to call Status = InsertInstalledApps(item); Are you sure the exception is not happening inside that method?

benjamin54 Over a year ago

No Error is from same line: var apps = JsonConvert.DeserializeObject<ApplicationObject>(jsonstring); I even added : ApplicationObject apps = new ApplicationObject(); Before that line. But no luck.

Leo Over a year ago

Sorry about that - try to change the property name from Applications to Application and see if it works. And you do not need to create ApplicationObject, DeserializeObject() will do it for you.

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