JSON.NET Serialize DateTime.MinValue as null
Solution 1
Create a custom converter which serializes DateTime.MinValue
into null
, and (if required) deserializes null
into DateTime.MinValue
:
public class MinDateTimeConverter : DateTimeConverterBase
{
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
if (reader.Value == null)
return DateTime.MinValue;
return (DateTime)reader.Value;
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
DateTime dateTimeValue = (DateTime)value;
if (dateTimeValue == DateTime.MinValue)
{
writer.WriteNull();
return;
}
writer.WriteValue(value);
}
}
You can then use attributes to add the converter to your data class, as shown in this example:
public class Example
{
[JsonConverter(typeof(MinDateTimeConverter))]
public DateTime ValueOne { get; set; }
[JsonConverter(typeof(MinDateTimeConverter))]
public DateTime ValueTwo { get; set; }
}
public static void Main(string[] args)
{
Example data = new Example();
data.ValueOne = DateTime.MinValue;
data.ValueTwo = DateTime.Now;
JsonSerializer serializer = new JsonSerializer();
using (StringWriter writer = new StringWriter())
{
serializer.Serialize(writer, data);
Console.Write(writer.ToString());
}
Console.ReadKey();
}
Console output:
{"ValueOne":null,"ValueTwo":"2016-10-26T09:54:48.497463+01:00"}
Solution 2
Custom DateTime Json Converter
public class DateTimeConverter : JsonConverter
{
public override void WriteJson(JsonWriter jsonWriter, object inputObject,JsonSerializer jsonSerializer)
{
// Typecast the input object
var dateTimeObject = inputObject as DateTime?;
// Set the properties of the Json Writer
jsonWriter.Formatting = Newtonsoft.Json.Formatting.Indented;
if(dateTimeObject == DateTime.MinValue)
jsonWriter.WriteValue((DateTime?)null);
else
jsonWriter.WriteValue(dateTimeObject);
}
public override object ReadJson(JsonReader reader,
Type objectType,
object existingValue,
JsonSerializer serializer)
{
DateTime? readValue = reader.ReadAsDateTime();
return (readValue == null) ? DateTime.MinValue : readValue;
}
public override bool CanConvert(Type objectType)
{
return typeof(DateTime?).IsAssignableFrom(objectType);
}
}
Usage:
public class DateTest
{
[JsonConverterAttribute(typeof(DateTimeConverter))]
public DateTime? MyDateTime { get; set;}
[JsonConverterAttribute(typeof(DateTimeConverter))]
public DateTime? MyDateTime1 { get; set; }
}
void Main()
{
DateTest dateTest = new DateTest
{
MyDateTime = DateTime.MinValue,
MyDateTime1 = DateTime.MaxValue
};
Console.WriteLine(JsonConvert.SerializeObject(dateTest));
}
Result:
{
"MyDateTime": null,
"MyDateTime1": "9999-12-31T23:59:59.9999999"
}
Solution 3
Not 100% clear on why the original poster wanted this and it's 5 years down the line but I too wanted to achieve this.
However, in my case the issue was that when I serialised my object it was inserting the DateTime fields because they hadn't been specified on the incoming object but were being returned as MinValue not null.
Thus when I deserialised at the other end these fields were showing as 'dirty' and being parsed.
In this case you can just amend your JsonSerializerSettings block to include 'ignore' in the default value handling:
string serialisedMessage = JsonConvert.SerializeObject(message, new JsonSerializerSettings
{
NullValueHandling = NullValueHandling.Ignore,
DefaultValueHandling = DefaultValueHandling.Ignore
});
So I'm leaving this in case of future users who are in my position.
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Mick
Microsoft Software developer with 20+ years experience and the plus just keeps on getting bigger.
Updated on September 15, 2022Comments
-
Mick over 1 year
I'd like
DateTime
fields that are set toDateTime.MinValue
returned by my Web API to be serialized toNULL
instead of"0001-01-01T00:00:00"
.I understand there's a way to get JSON.NET to omit fields that are set to default values, but I would prefer JSON.NET to specifically serialize
DateTime MinValue / "0001-01-01T00:00:00" as null
.Is there a way to do this?
-
dbc over 7 years
DateTimeConverterBase
also acceptsDateTimeOffset
so you need to modifyCanConvert
to only return true forDateTime
andDateTime?
-
Alsty over 7 years@dbc This converter will only work when directly applied to
DateTime
properties using aJsonConverter
attribute.CanConvert
is not called in this scenario.ReadJson
would need to be modified ifDateTime?
types need to be supported.