I'm closing this question without answer, because it's duplicate of this: Serializing null in JSON.NET
I'm writing a simple converter which reads null as DateTime.UtcNow and writes null as DateTime.UtcNow.ToString("o"). It could be like this:
public class NullableDateTimeConverter : JsonConverter
{
public override bool CanConvert(Type objectType)
{
//Console.WriteLine("object type: " + objectType.Name);
return objectType == typeof(DateTime?);
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
if (reader.Value == null)
{
return DateTime.Now;
}
else
{
return (DateTime?)reader.Value;
}
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
if (value == null)
{
serializer.Serialize(writer, DateTime.UtcNow.ToString("o"));
}
else
{
serializer.Serialize(writer, ((DateTime?)value).Value.ToString("o"));
}
}
}
Now, I'm trying to serialize, and deserialize this object.
public class NullableDateTimeObject
{
public DateTime? Value { get; set; }
}
Like this:
public static void Main()
{
var settings = new JsonSerializerSettings();
settings.NullValueHandling = NullValueHandling.Include;
settings.DefaultValueHandling = DefaultValueHandling.Include;
settings.Converters.Add(new NullableDateTimeConverter());
Console.WriteLine("------- not null -------");
var result1 = JsonConvert.SerializeObject(
new NullableDateTimeObject { Value = DateTime.UtcNow },
settings);
Console.WriteLine(result1);
Console.WriteLine("------- null -------");
var result2 = JsonConvert.SerializeObject(
new NullableDateTimeObject { Value = null },
settings);
Console.WriteLine(result2);
Console.WriteLine("------- but it reads null -------");
var resultRead = JsonConvert.DeserializeObject<NullableDateTimeObject>(
"{\"Value\":null}",
settings);
Console.WriteLine(resultRead.Value);
}
I expected that the second one also writes ISO8601 datetime, but it writes null.
------- not null -------
{"Value":"2017-02-25T13:04:13.3091219Z"}
------- null -------
{"Value":null}
------- but it reads null -------
2/25/2017 1:14:56 PM
The JsonConverter doesn't even call CanConvert() override for a null value of property, when it serializes an object. In other hands, it works as I expected when it deserializes an object.
Does it an expected behavior? How can I make to use JsonConverter for a null value?
+I made a fiddle to reproduce it: https://dotnetfiddle.net/5PLvsk
[Added]
I also tested with explicit JsonConverter for the property, just in case, like this:
public class NullableDateTimeObjectWithExplicitConverter
{
[JsonConverter(typeof(NullableDateTimeConverter))]
[JsonProperty(IsReference = true, DefaultValueHandling = DefaultValueHandling.Populate, NullValueHandling = NullValueHandling.Include)]
public DateTime? Value { get; set; }
}
Console.WriteLine("------- explicit converter -------");
var result3 = JsonConvert.SerializeObject(
new NullableDateTimeObjectWithExplicitConverter { Value = null },
settings);
Console.WriteLine(result3);
The result is same, null.
------- explicit converter -------
{"Value":null}
Even if the explicit one worked, but the JsonConverterSettings should be working recursively, I think.
