C#•12mo ago

❔ How to serialize certain null values with System.Text.Json

In System.Text.Json, if I have something like

record Item(string Text, int? Number);

List<Item> items = new();
JsonSerializerOptions options = new() {
    DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingDefault,
};
string json = JsonSerializer.Serialize(items, options);

record Item(string Text, int? Number);

List<Item> items = new();
JsonSerializerOptions options = new() {
    DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingDefault,
};
string json = JsonSerializer.Serialize(items, options);

I can serialize a list of items but ignore null values when writing, but what should I do if I want to serialize a single null value and ignore all others, something like this:

[
{
  "Text": "Test"
},
{
  "Text": "test 2",
  "Number": 1
},
{
  "Text": "test 3",
  "Number": null, // Tell the serializer to only serialize this null value
}
]

[
{
  "Text": "Test"
},
{
  "Text": "test 2",
  "Number": 1
},
{
  "Text": "test 3",
  "Number": null, // Tell the serializer to only serialize this null value
}
]

4 Replies

artya•12mo ago

I misread your question 🤦

Chik3r•12mo ago

Always and Never wouldnt work since I only want to write it in some conditions (Text matches x value or some other condition) WhenWritingDefault would ignore all null values and WhenWritingNull wouldnt let me write null

Kouhai•12mo ago

You need a custom converter

Accord•12mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ How to serialize certain null values with System.Text.Json