Deserializing a JSON object hierarchy into a hierarchy of Dictionary<string, object>

Question

I'm in .NET for WinRT (C#) and I'd like to deserialize a JSON string to a Dictionary<string, object>, where the dictionary value can later be converted to the actual type. The JSON string can contain an object hierarchy and I'd like to have child objects in Dictionary<string, object> as well.

Here's a sample JSON it should be able to handle:

{
  "Name":"John Smith",
  "Age":42,
  "Parent":
  {
    "Name":"Brian Smith",
    "Age":65,
    "Parent":
    {
       "Name":"James Smith",
       "Age":87,
    }
  }
}

I tried with the DataContractJsonSerializer doing as so:

using (MemoryStream ms = new MemoryStream(Encoding.UTF8.GetBytes(json)))
{
    DataContractJsonSerializerSettings settings = new DataContractJsonSerializerSettings();
    settings.UseSimpleDictionaryFormat = true;

    DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(Dictionary<string, object>), settings);
    Dictionary<string, object> results = (Dictionary<string, object>)serializer.ReadObject(ms);
}

This actually works fine for the first level, but then "Parent" is just an object which cannot be casted to a Dictionary<string, object>:

Dictionary<string, object> parent = (Dictionary<string, object>)results["Parent"];
Cannot cast 'results["Parent"]' (which has an actual type of 'object') to 'System.Collections.Generic.Dictionary<string,object>'

I then tried using Json.NET but child objects are JObject themselves being IDictionary<string, JToken>, which forces me to iterate through the full hierarchy and convert them over again.

Would someone know how to solve this problem using an existing serializer?

EDIT

I'm using Dictionary<string, object> because my objects vary from one server call to another (e.g. the "Id" property might be "id", *"cust_id"* or "customerId" depending on the request) and as my app isn't the only app using those services, I can't change that, at least for now.

Therefore, I found it inconvenient to use DataContractAttribute and DataMemberAttribute in this situation. Instead I'd like to store everything in a generic dictionary, and have a single strongly-typed property "Id" which looks for "id", "cust_id" or "customerId" in the dictionary making it transparent for the UI.

This system works great with JSON.NET, however if ever the server returns an object hierarchy, sub-objects will be stored as JObjects in my dictionary instead of another dictionary.

To sum-up, I'm looking for an efficient system to transform an object hierarchy into a hierarchy of Dictionary<string, object> using a JSON serializer available in WinRT.

Chris Moutray · Accepted Answer · 2014-01-09 09:28:13Z

4

I'm addressing this same issue in a WinRT app using a combination of the JSON.NET library and the ExpandoObject class. The library is able to deserialize JSON data quite nicely into ExpandoObjects, which implement IDictionary. The value of an ExpandoObject's key-value pair may easily be treated as another ExpandoObject.

Here's the approach I used, adapted to your sample:

void LoadJSONData()
{
    string testData = "{ \"Name\":\"John Smith\", \"Age\":42, \"Parent\": { \"Name\":\"Brian Smith\", \"Age\":65, \"Parent\": { \"Name\":\"James Smith\", \"Age\":87, } } }";

    ExpandoObject dataObj = JsonConvert.DeserializeObject<ExpandoObject>(testData, new ExpandoObjectConverter());

    // Grab the parent object directly (if it exists) and treat as ExpandoObject
    var parentElement = dataObj.Where(el => el.Key == "Parent").FirstOrDefault();
    if (parentElement.Value != null && parentElement.Value is ExpandoObject)
    {
        ExpandoObject parentObj = (ExpandoObject)parentElement.Value;
        // do something with the parent object...
    }

    // Alternately, iterate through the properties of the expando
    foreach (var property in (IDictionary<String, Object>)dataObj)
    {
        if (property.Key == "Parent" && property.Value != null && property.Value is ExpandoObject)
        {
            foreach (var parentProp in (ExpandoObject)property.Value)
            {
                // do something with the properties in the parent expando
            }
        }
    }
}

edited Jan 9, 2014 at 9:28

Chris Moutray

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answered Nov 30, 2012 at 17:12

SWalters

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1 Comment

canderso Over a year ago

Very interesting, it looks like what I'm looking for. I'll give it a try today and see if it fits (functionally and perf-wise)!

Furqan Safdar · Accepted Answer · 2012-11-30 07:15:39Z

3

Try this piece of code snippet:

var d = new System.Web.Script.Serialization.JavaScriptSerializer();
var results = d.Deserialize<Dictionary<string, object>>(jsonString);
var parent = (Dictionary<string, object>)results["Parent"];

According to the reference, JavaScriptSerializer Class supports Windows 8.

For deserialization, Json.NET is also an option to be considered with Windows 8 support.

ADDED, For WinRT:

Define the DataContract according to your JSON.

[DataContract]
public class CustomObject
{
    [DataMember(Name = "Name")]
    public string Name { get; set; }

    [DataMember(Name = "Age")]
    public string Age { get; set; }

    [DataMember(Name = "Parent")]
    public Dictionary<string, object> Parent { get; set; }
}

Use the DataContract class while deserialization.

using (MemoryStream ms = new MemoryStream(Encoding.UTF8.GetBytes(json)))
{
    DataContractJsonSerializerSettings settings = 
            new DataContractJsonSerializerSettings();
    settings.UseSimpleDictionaryFormat = true;

    DataContractJsonSerializer serializer = 
            new DataContractJsonSerializer(typeof(CustomObject), settings);

    CustomObject results = (CustomObject)serializer.ReadObject(ms);
    Dictionary<string, object> parent = results.Parent;
}

Reference: Creating .NET objects from JSON using DataContractJsonSerializer

edited Nov 30, 2012 at 7:15

answered Nov 29, 2012 at 17:26

Furqan Safdar

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6 Comments

fsimonazzi Over a year ago

Note that the type is included in the System.Web.Extensions assembly. Is it available to WinRT apps?

Furqan Safdar Over a year ago

As per my findings so far ... yes, msdn.microsoft.com/en-us/library/… and msdn.microsoft.com/en-us/library/…

fsimonazzi Over a year ago

Mmmm, it does not show up in the list of supported APIs msdn.microsoft.com/en-us/library/windows/apps/br230232.aspx

fsimonazzi Over a year ago

.NET running on a Windows 8 host != WinRT .NET app.

canderso Over a year ago

Thanks but the System.Web namespace isn't available in .NET for WinRT. Regarding solution number two, it works in this scenario as all objects of hierarchy are the same, but that's not always the case in my real app (hence the use of a Dictionary<string, object> btw).

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