c# - Deserialization problem with DataContractJsonSerializer

Question

I've got the following piece of JSON:

[{
    "name": "numToRetrieve",
    "value": "3",
    "label": "Number of items to retrieve:",
    "items": {
        "1": "1",
        "3": "3",
        "5": "5"
    },
    "rules": {
        "range": "1-2"
    }
},
{
    "name": "showFoo",
    "value": "on",
    "label": "Show foo?"
},
{
    "name": "title",
    "value": "Foo",
    "label": "Foo:"
}]

All in one line version (suitable for a string literal):

[{"name":"numToRetrieve","value":"3","label":"Number of items to retrieve:","items":{"1":"1","3":"3","5":"5"},"rules":{"range":"1-2"}},{"name":"showFoo","value":"on","label":"Show foo?"},{"name":"title","value":"Foo","label":"Foo:"}]

In the above example, name, value, and label are required but items and rules are optional.

Here's the class I'm trying to deserialize into:

using System.Collections;
using System.Collections.Generic;
using System.Runtime.Serialization;

namespace foofoo
{
    [DataContract]
    public sealed class FooDef
    {
        [DataMember(Name = "name", IsRequired = true)]
        public string Name { get; set; }

        [DataMember(Name = "value", IsRequired = true)]
        public string Value { get; set; }

        [DataMember(Name = "label", IsRequired = true)]
        public string Label { get; set; }

        [DataMember(Name = "items", IsRequired = false)]
        public Dictionary<string, string> Items { get; set; }

        [DataMember(Name = "rules", IsRequired = false)]
        public Dictionary<string, string> Rules { get; set; }
    }
}

Here's the code I use to deserialize:

var json = new DataContractJsonSerializer(typeof(List<FooDef>));
var bar = "[{"name":"numToRetrieve","value":"3","label":"Number of items to retrieve:","items":{"1":"1","3":"3","5":"5"},"rules":{"range":"1-2"}},{"name":"showFoo","value":"on","label":"Show foo?"},{"name":"title","value":"Foo","label":"Foo:"}]";
var stream = new MemoryStream(Encoding.UTF8.GetBytes(bar));
var foo = json.ReadObject(stream);
stream.Close();

Everything goes reasonably well except that items and rules are empty for the first FooDef pass. I have tried everything under the sun to try and get them populated: custom classes, NameValueCollection, KeyValuePair<string, string>, List of both of the latter, and every other collection that seemed to apply. [EDIT: I forgot to try Hashtable, which seemed like an obvious candidate. Didn't work.]

The problem, as I see it, is that the key piece under items and rules is open-ended. That is, it's not always going to be called range or 3. Any advice or ideas?

Answer 1

IMHO there is no way to deserialize the JSON string you provided into a .NET class using DataContractJsonSerializer.

The problem comes from the way DataContractJsonSerializer serializes dictionaries. You could use an alternative serializer such as Json.NET (which I strongly recommend) or JavaScriptSerializer (I think it was deprecated in favor of DataContractJsonSerializer but it will work for your scenario).

You can also read these rants.

Documentation: Serializing Collections - Json.NET