JSON.NET NullValueHandling in JsonPropertyAttribute not working as expected

Question

I have a class like so:

[JsonObject]
public class Condition
{
    [JsonProperty(PropertyName = "_id")]
    public string Id { get; set; }

    [JsonProperty(PropertyName = "expressions", NullValueHandling = NullValueHandling.Ignore)]
    public IEnumerable<Expression> Expressions { get; set; }

    [JsonProperty(PropertyName = "logical_operation")]
    [JsonConverter(typeof(StringEnumConverter))]
    public LogicOp? LogicalOperation { get; set; }

    [JsonProperty(PropertyName = "_type")]
    [JsonConverter(typeof(AssessmentExpressionTypeConverter))]
    public ExpressionType Type { get; set; }
}

However, when the Expressions property is null, and I serialize the object like so:

 var serialized = JsonConvert.SerializeObject(condition, Formatting.Indented);

... the text of the Json string has the line:

"expressions": null

My understanding is that this should not happen. What am I doing wrong?

Have you solved this? Running into same problem, the attribute on the property has no effect. — Jacek Gorgoń, Aug 23 '15 at 16:10
In my case, the serialization of that object was overriden with a custom `CustomCreationConverter`, but you could also see this: http://stackoverflow.com/questions/8424151/json-net-serializer-ignoring-jsonproperty?rq=1 — Jacek Gorgoń, Aug 23 '15 at 18:20

score 4 · Answer 1 · answered Mar 13 '22 at 22:46

The default text serializer used by .net API is System.Text.Json:

https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json-customize-properties?pivots=dotnet-6-0

So if you want to ignore if null you can use:

[JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]

Example:

public class Forecast
{
    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]
    public DateTime Date { get; set; }

    [JsonIgnore(Condition = JsonIgnoreCondition.Never)]
    public int TemperatureC { get; set; }

    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
    public string? Summary { get; set; }
}

This question is 7 years old; at the time it was asked, JSON.NET was the de facto JSON serializer. — Jeremy Holovacs, Mar 14 '22 at 23:29

score 1 · Answer 2 · answered May 01 '19 at 22:31

1

You may use [JsonProperty(NullValueHandling=NullValueHandling.Ignore)] instead

answered May 01 '19 at 22:31

Kush

438
1
7
20

score 1 · Answer 3 · answered Sep 30 '20 at 09:35

1

add this service on Startup.cs :

services.AddControllersWithViews().AddJsonOptions(options =>
{
    options.JsonSerializerOptions.IgnoreNullValues = true;
});

answered Sep 30 '20 at 09:35

Reza Ahmadi

41
5

score 0 · Answer 4 · answered Mar 23 '15 at 19:25

0

Try passing new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore } as third parameter in JsonConvert.SerializeObject method.

answered Mar 23 '15 at 19:25

Manoj Gupta

1
1

1

Hmmm... there are quite a few properties that I *do* want to render as `null` though, and I think that will apply a blanket policy for the entire serialization. – Jeremy Holovacs Mar 23 '15 at 19:26

JSON.NET NullValueHandling in JsonPropertyAttribute not working as expected

4 Answers4