JsonIgnoreCondition
Controls how the JsonIgnoreAttribute ignores properties on serialization and deserialization.
Always = 1
Property will always be ignored.
Never = 0
Property will always be serialized and deserialized, regardless of IgnoreNullValues configuration.
Property will only be ignored if it is null.
WhenWritingNull = 3
If the value is null, the property is ignored during serialization. This is applied only to reference-type properties and fields.