Ignore boolean property = true in JSON serialization

Question

I have a record with a bool property that has default value = true:

private record MyRecord()
{
    public bool BoolProperty { get; init; } = true;
}

I want to ignore the "BoolProperty":true in the serialized JSON string. In other words if the BoolProperty is true, I want this property to be omitted from the resulting JSON representation. Is this possible?

Here is a demonstration of the desirable behavior:

JsonSerializerOptions options = new();
options.DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingDefault;

MyRecord obj = new();
Console.WriteLine($"Object: {obj}"); // OK
string json = JsonSerializer.Serialize(obj, options);
Console.WriteLine($"JSON: {json}"); // Not OK

The output is:

Object: MyRecord { BoolProperty = True }
JSON: {"BoolProperty":true}

The desirable output should be:

Object: MyRecord { BoolProperty = True }
JSON: {}

Online demo.

I searched for a duplicate question and I didn't find any.

Guru Stron · Accepted Answer · 2025-11-11 16:44:52Z

4

You can try customizing the serialization properties via a modifier which will analyze type and property:

var serializerOptions = new JsonSerializerOptions
{
    TypeInfoResolver = new DefaultJsonTypeInfoResolver
    {
        Modifiers =
        {
            info =>
            {
                if (info.Type == typeof(MyRecord))
                {
                    foreach (var jPropInf in info.Properties)
                    {
                        if (jPropInf.Name == nameof(MyRecord.BoolProperty) 
                            && jPropInf.PropertyType == typeof(bool))
                        {
                            jPropInf.ShouldSerialize = 
                                 (_, str) => str is bool and is false;
                        }
                    }
                }
            }
        }
    }
};

var serialized = JsonSerializer.Serialize(new MyRecord(), serializerOptions);
Console.WriteLine(serialized); // prints "{}"

Check out the Customize a JSON contract doc.

answered Nov 11 at 16:44

Guru Stron

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3 Comments

Theodor Zoulias Nov 11 at 16:55

Excellent! Thanks Guru Stron for the quick answer.

Theodor Zoulias Nov 11 at 17:47

Follow up question here, with 200 bounty points for a correct answer (as soon as starting the bounty is possible).

Guru Stron Nov 11 at 18:03

Yep, I've tried that one too =)

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