How to force JSON.NET to serialize null values in a dictionary as undefined keyword

Asked May 27 '19 at 09:59

Active May 27 '19 at 10:18

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There is a Dictionary where some values are primitive boxed values (bool, int, decimal) and others are null and DBNull.Value. Is it possible to output serialized JSON with undefined keyword for the latter category of entries using JSON.NET?

I was trying to set NullValueHandling.Ignore but that removes null-ed property completely. An implementation of JsonConverter does not help as it is not used on null value.

To illustrate my question consider this object

var toSerialize = new Dictionary<string, object> = 
{
    {"key1": 1}, 
    {"key2": true}, 
    {"key3": DBNull.Value}, 
    {"key4": null}
};

The result should be as

{
  "key1": 1, 
  "key2": true, 
  "key3": undefined, 
  "key4": undefined
}

and not as

{
  "key1": 1, 
  "key2": true, 
  "key3": null, 
  "key4": null
}

the indentation is not important. Thanks.

asked May 27 '19 at 09:59

Mx.Wolf

6

`undefined` does not exist in json. Only numbers, floats, strings, booleans, objects, arrays and null are valid json entries – Patrick Hollweck May 27 '19 at 10:04
AFAIK, an empty object `{}` is considered as `undefined`. – StackLloyd May 27 '19 at 10:10
`{}` does not considered as `undefined` by the test like `typeof va === "undefined"` – Mx.Wolf May 27 '19 at 10:14
Does `null` count for that test? – Lasse V. Karlsen May 27 '19 at 10:29
And no, `undefined` is not legal json, you will not be able to serialize to that in C#. You will have to find some other way of reaching your goal. – Lasse V. Karlsen May 27 '19 at 10:30
The desired target is `{ "key1": 1, "key2": true }`. The duplicate shows how to do that. – mjwills May 27 '19 at 10:34

How to force JSON.NET to serialize null values in a dictionary as undefined keyword

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