How to ignore default values while serializing json with Newtonsoft.Json

Question

I'm using Newtonsoft.Json.JsonConvert to serialize a Textbox (WinForms) into json and I want the serialization to skip properties with default values or empty arrays.

I'v tried to use NullValueHandling = NullValueHandling.Ignore in JsonSerializerSettings but is doesn't seem to affect anything.

Here is the full code sample (simplified):

JsonSerializerSettings settings = new JsonSerializerSettings()
                {
                    Formatting = Formatting.None,
                    DefaultValueHandling = DefaultValueHandling.Ignore,
                    NullValueHandling = NullValueHandling.Ignore,
                    ReferenceLoopHandling = ReferenceLoopHandling.Ignore,
                    ObjectCreationHandling = ObjectCreationHandling.Replace,
                    PreserveReferencesHandling = PreserveReferencesHandling.None,
                    ConstructorHandling = ConstructorHandling.AllowNonPublicDefaultConstructor,
                };

    string json = JsonConvert.SerializeObject(textbox, settings);

Any ideas ?

Answer 1

You could use the standard conditional-serialization pattern:

private int bar = 6; // default value of 6
public int Bar { get { return bar;} set { bar = value;}}
public bool ShouldSerializeBar()
{
    return Bar != 6;
}

The key is a public bool ShouldSerialize*() method, where * is the member-name. This pattern is also used by XmlSerializer, protobuf-net, PropertyDescriptor, etc.

This does, of course, mean you need access to the type.