Question

I have a RESTful webservice which receives JSON and it deserialises it into a c# class using the DataContractJsonSerializer, though this can be changed.

Its purpose is to update fields on a resource

e.g.:

{
    "firstName" : "Martin"
}

I don’t necessarily want to update all the fields, and I was hoping to find a way to detect fields which are and are not unspecified in the JSON.

I can’t find a way to do this however because I don’t know how to tell the difference between an unspecified field and a field which should be updated to null

e.g: (don’t update any fields):

{}

vs: (update the firstName field to null)

{
    "firstName" : null
}

What is the best way to approach this?

Answer 1

I think you can use a field initialized with some random string

public class TestClass
{
    public string firstName = "some string";
}

If you deserialize using {"firstName" : null}, firstName will be null. if you deserialize using {} firstName won’t change (some string)

PS: Don’t use DataContract or DataMember attributes if you are using DataContractJsonSerializer