Handling enums in JSON

Question

When I serialize an object of a class with a enum property to JSON, if the value is null, the resulting json string has a name value pair like this:

"controlType":"-2147483648"

This causes issues when I deserialize the string to a strongly typed object.

What's the best way of handling enums and nulls?

Answer 1

Consider:

echo json_encode(array("test"=>null));

This produces:

{"test":null}

The best way to handle enums is with a key,value array or an stdClass. Just bind your names to a set of unique integers. You can then bind the other direction as well:

{"A":1, "B":2, "C":3, 1:"A", 2:"B", 3:"C"}

This at least gives you bi-directionality.

Answer 2

the below code gives you json = '{"Name":"Test","Id":1,"MyEnum":3}', when you have a non-null value.

     public enum SerializeObjTestClassEnum
 {
  one = 1, two, three, four
 }

 [Serializable]
 public class SerializeObjTestClass
 {
  public string Name { get; set; }
  public int Id { get; set; }
  public SerializeObjTestClassEnum MyEnum{ get; set; }
 }

 public void SerializeObject_Test_Basic_Object()
 {
  var obj = new SerializeObjTestClass { Id = 1, Name = "Test", MyEnum = SerializeObjTestClassEnum.three };
  var json = (new JavaScriptSerializer()).Serialize(obj);
 }

---

this code gives you json = '{"Name":"Test","Id":1,"MyEnum":0}'

    var obj = new SerializeObjTestClass { Id = 1, Name = "Test" };

Notice how the enum, when not set, is serialized to a 0, while the enum itself starts out at 1. So this is how you code can know a NULL value was used for the enum.

if you want the json to look like '{"Name":"Test","Id":1,"MyEnum":null}', then you're going to need to fake it out by using a class wrapper around the Enum.