Json.NET - prevent re-serializing an already-serialized property [duplicate]

Question

In an ASP.NET Web API application, some of the models I'm working with contain a chunk of ad-hoc JSON that is useful only on the client side. On the server it simply goes in and out of a relational database as a string. Performance is key, and it seems pointless to process the JSON string server side at all.

So in C#, imagine an object like this:

new Person
{
    FirstName = "John",
    LastName = "Smith",
    Json = "{ \"Age\": 30 }"
};

By default, Json.NET will serialize this object like this:

{
    "FirstName": "John",
    "LastName": "Smith",
    "Json": "{ \"Age\": 30 }"
}

I'd like to be able to instruct Json.NET to assume that the Json property is already a serialized representation, thus it shouldn't re-serialize, and the resulting JSON should look like this:

{
    "FirstName": "John",
    "LastName": "Smith",
    "Json": {
        "Age": 30
    }
}

Ideally this works in both directions, i.e. when POSTing the JSON representation it will automatically deserialize to the C# representation above.

What is the best mechanism to achieve this with Json.NET? Do I need a custom JsonConverter? Is there a simpler attribute-based mechanism? Efficiency matters; the whole point is to skip the serialization overhead, which could be a bit of a micro-optimization, but for argument's sake let's assume it's not. (There will potentially be big lists with bulky Json properties being returned.)

Answer 1

If you are able to change the type of the Json property on Person from string to JRaw then you will get the desired result.

public class Person
{
    public string FirstName { get; set;}
    public string LastName { get; set;}        
    public JRaw Json  { get; set;}
} 

Alternatively, you could keep the string property, and add a JRaw property to be used as a proxy for serialization:

public class Person
{
    public string FirstName { get; set;}
    public string LastName { get; set;}
    [JsonIgnore]
    public string Json { get; set; }

    [JsonProperty("Json")]
    private JRaw MyJson
    {
        get { return new JRaw(this.Json); }
        set { this.Json = value.ToString(); }
    }        
}

Either way, both serialization and deserialization will work as you have requested.