deserialize json in C# with illegal variable characters

Question

I'm writing a .NET library (using Newtonsoft) that interacts with a REST service, and I have a service that's returning json, but the json id field is called '$id'. So I can't just create a corresponding $id property in my C# data class. I tried to use something like

    [JsonObject(MemberSerialization.OptOut)]
    public class DocData
    {
        [JsonProperty("$id")]
        public string id { get; set; }

        public string Name { get; set; }
    }

but while Name gets assigned, the id property does not. Anyone know how to map this json key to .NET?

Thanks

Answer 1

It looks like this is a bug in JSON.NET, and I think you should report it. It works fine in LINQPad for any property name except $id.

void Main()
{
    var s = JsonConvert.SerializeObject(new DocData{id = "hi", Name = "world"}).Dump();
    JsonConvert.DeserializeObject<DocData>(s).Dump();
}

public class DocData
{
    // [JsonProperty("i$d")] // this would work 
    // [JsonProperty("_id")] // as would this
    // [JsonProperty("$name")] // and even this
    [JsonProperty("$id")] // but this fails
    public string id { get; set; }

    public string Name { get; set; }
}

Evidently Json.NET uses $id as a reserved word to help it deal with object references.

    var dd = new DocData{id = "hi", Name = "world"};
    JsonConvert.SerializeObject(new[]{dd, dd}, new JsonSerializerSettings{PreserveReferencesHandling = PreserveReferencesHandling.Objects}).Dump();
// Output: [{"$id":"1","$id":"hi","Name":"world"},{"$ref":"1"}]

Still, it seems like it should let you capture the $id property if you're not using reference handling.

As a workaround, you can parse it into a JObject, and pull the property out directly:

    var id = JObject.Parse(s)["$id"];
    var obj = JsonConvert.DeserializeObject<DocData>(s);
    obj.id = id;