Json.net serialize only certain properties

Question

Does Json.net have any way to specify only the properties you want to be serialized? or alternatively serialize certain properties based on binding flags like Declared Only?

Right now I am using JObject.FromObject(MainObj.SubObj); to get all properties of SubObj which is an instance of a class that obeys the ISubObject interface:

public interface ISubObject
{

}

public class ParentSubObject : ISubObject
{
    public string A { get; set; }
}


public class SubObjectWithOnlyDeclared : ParentSubObject
{
    [JsonInclude] // This is fake, but what I am wishing existed
    public string B { get; set; }

    [JsonInclude] // This is fake, but what I am wishing existed
    public string C { get; set; }
}

public class NormalSubObject: ParentSubObject
{
    public string B { get; set; }
}

If MainObj.SubObj was a NormalSubObject it would serailize both A and B but if it was SubObjectWithOnlyDeclared it would serailize only B and C and ignore the parent property

Checkout this article on conditional serialization. I found it useful. geekytidbits.com/conditional-serialization-with-json-net — Rich
– Rich, Commented Jun 21, 2018 at 18:33

Alfie · Accepted Answer · 2019-03-07 14:31:36Z

56

Rather then having to use [JsonIgnore] on every attribtue you don't want to serialise as suggested in another answer.

If you just want to specify properties to serialise, you can do this, using [JsonObject(MemberSerialization.OptIn)] and [JsonProperty] attributes, like so:

using Newtonsoft.Json;
...
[JsonObject(MemberSerialization.OptIn)]
public class Class1
{
    [JsonProperty]
    public string Property1 { set; get; }
    public string Property2 { set; get; }
}

Here only Property1 would be serialised.

answered Mar 7, 2019 at 14:31

Alfie

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1 Comment

JKennedy Over a year ago

This should be the selected answer

Eser · Accepted Answer · 2018-06-21 19:21:21Z

You can write a custom ContractResolver like below

public class IgnoreParentPropertiesResolver : DefaultContractResolver
{
    bool IgnoreBase = false;
    public IgnoreParentPropertiesResolver(bool ignoreBase)
    {
        IgnoreBase = ignoreBase;
    }
    protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
    {
        var allProps = base.CreateProperties(type, memberSerialization);
        if (!IgnoreBase) return allProps;

        //Choose the properties you want to serialize/deserialize
        var props = type.GetProperties(~BindingFlags.FlattenHierarchy); 

        return allProps.Where(p => props.Any(a => a.Name == p.PropertyName)).ToList();
    }
}

Now you can use it in your serialization process as:

var settings = new JsonSerializerSettings() { 
                      ContractResolver = new IgnoreParentPropertiesResolver(true) 
               };
var json1 = JsonConvert.SerializeObject(new SubObjectWithOnlyDeclared(),settings );

Atif Rehman · Accepted Answer · 2020-06-19 19:14:49Z

3

If you have a property on your object that is null or the default value, you can let json.net ignore it and NOT serialize it by:

var settings = new JsonSerializerSettings 
{
    DefaultValueHandling = DefaultValueHandling.Ignore, NullValueHandling = NullValueHandling.Ignore
};

JsonConvert.SerializeObject(myObject, settings);

EDIT:

Or global default setting, do this once:

JsonConvert.DefaultSettings = () => new JsonSerializerSettings 
{
    DefaultValueHandling = DefaultValueHandling.Ignore, NullValueHandling = NullValueHandling.Ignore
};

edited Jun 19, 2020 at 19:14

answered Jun 19, 2020 at 19:00

Atif Rehman

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Comments

Aydin · Accepted Answer · 2018-06-21 18:03:07Z

2

Not sure why @Eser chose to write the answer as comment to your question as opposed to an actual answer... anyway, they're correct.

Apply the [JsonIgnore] attribute to any property that you want to ignore.

answered Jun 21, 2018 at 18:03

Aydin

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1 Comment

CuriousDeveloper Over a year ago

This isnt an acceptable answer though, I would need to conditionally ignore public string A { get; set; } because in one scenario I dont want it ignored, and in another I do.

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