Ignoring null fields in Json.net

Question

I have some data that I have to serialize to JSON. I'm using JSON.NET. My code structure is similar to this:

public struct structA
{
    public string Field1;
    public structB Field2;
    public structB Field3;
}

public struct structB
{
    public string Subfield1;
    public string Subfield2;
}

Problem is, my JSON output needs to have ONLY Field1 OR Field2 OR Field3 - it depends on which field is used (i.e. not null). By default, my JSON looks like this:

{
    "Field1": null,
    "Field2": {"Subfield1": "test1", "Subfield2": "test2"},
    "Field3": {"Subfield1": null, "Subfield2": null},
}

I know I can use NullValueHandling.Ignore, but that gives me JSON that looks like this:

{
    "Field2": {"Subfield1": "test1", "Subfield2": "test2"},
    "Field3": {}
}

And what I need is this:

{
    "Field2": {"Subfield1": "test1", "Subfield2": "test2"},
}

Is there simple way to achieve this?

Possible duplicate of How to ignore a property in class if null, using json.net — Michael Freidgeim
– Michael Freidgeim, Commented Aug 12, 2016 at 8:20
Because you are using structs, the only field that may have a null value is Field1. If you want Field2 and Field3 to be nulllable, you need to make them reference types instead of value types. — Suncat2000
– Suncat2000, Commented Aug 16, 2021 at 15:07

James Newton-King · Accepted Answer · 2015-01-30 20:46:24Z

80

Yes you need to use JsonSerializerSettings.NullValueHandling = NullValueHandling.Ignore.

But because structs are value types you need to mark Field2, Field3 nullable to get the expected result:

public struct structA
{
    public string Field1;
    public structB? Field2;
    public structB? Field3;
}

Or just use classes instead of structs.

Documentation: NullValueHandling Enumeration

edited Jan 30, 2015 at 20:46

James Newton-King

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answered Mar 22, 2012 at 9:51

nemesv

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1 Comment

Mickey Perlstein Over a year ago

for more info see james.newtonking.com/archive/2009/10/23/…

SuperStormer · Accepted Answer · 2021-12-11 01:52:55Z

78

You can also apply the JsonProperty attribute to the relevant properties and set the null value handling that way. Refer to the Reference property in the example below:

Note: The JsonSerializerSettings will override the attributes.

public class Person
{
    public int Id { get; set; }
    
    [JsonProperty( NullValueHandling = NullValueHandling.Ignore )]
    public int? Reference { get; set; }

    public string Name { get; set; }
}

edited Dec 11, 2021 at 1:52

SuperStormer

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answered Feb 26, 2014 at 11:14

Jaans

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