Problems with Json Serialize Dictionary<Enum, Int32>

Question

whenever i try to serialize the dictionary i get the exception:

System.ArgumentException: Type 
'System.Collections.Generic.Dictionary`2[[Foo.DictionarySerializationTest+TestEnum, Foo, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]'
is not supported for serialization/deserialization of a dictionary,
keys must be strings or object

My Testcase is:

public class DictionarySerializationTest
{
  public enum TestEnum { A, B, C }
  //tried with numbers, too: public enum TestEnum { A = 1, B = 2, C = 3 }

  public void SerializationTest()
  {
    Dictionary<TestEnum, Int32> data = new Dictionary<TestEnum, Int32>();

    data.Add(TestEnum.A, 1);
    data.Add(TestEnum.B, 2);
    data.Add(TestEnum.C, 3);

    JavaScriptSerializer serializer = new JavaScriptSerializer();
    String result = serializer.Serialize(data);
    // Throws
  }

  public void SerializationToObjectTest()
  {
    Dictionary<object, Int32> data = new Dictionary<object, Int32>();

    data.Add(Enum.ToObject(typeof(TestEnum), TestEnum.A), 1);
    data.Add(Enum.ToObject(typeof(TestEnum), TestEnum.B), 2);
    data.Add(Enum.ToObject(typeof(TestEnum), TestEnum.C), 3);

    JavaScriptSerializer serializer = new JavaScriptSerializer();
    String result = serializer.Serialize(data);
    // Throws
  }

  public void SerializationStringTest()
  {
    Dictionary<String, Int32> data = new Dictionary<String, Int32>();

    data.Add(TestEnum.A.ToString(), 1);
    data.Add(TestEnum.B.ToString(), 2);
    data.Add(TestEnum.C.ToString(), 3);

    JavaScriptSerializer serializer = new JavaScriptSerializer();
    String result = serializer.Serialize(data);
    // Succeeds
  }

}

Of course i could use .ToString() whenever i enter something into the Dictionary but since it's used quite often in performance relevant methods i would prefer using the enum.

My only solution is using .ToString() and converting before entering the performance critical regions but that is clumsy and i would have to change my code structure just to be able to serialize the data.

Does anyone have an idea how i could serialize the dictionary as <Enum, Int32>?

I use the System.Web.Script.Serialization.JavaScriptSerializer for serialization.

UPDATE:

I switched to Dictionary<String, Int32> now and it works but i hope someone shows a solution as i don't really like using strings in place of a type safe enum.

Answer 1

Use Newtonsoft (Newtonsoft.Json.dll) to serialize the Dictionary object and you'd be fine. It's a popular third party library you would have to download and include in your project as a reference.

See example below:

var _validationInfos = new Dictionary<ImportField, ValidationInfo>();
var serializedData = JsonConvert.SerializeObject(_validationInfos);

Answer 2

I know it's late, but maybe someone else can make use of it in the future. You can achieve what you need using LINQ:

Dictionary<TestEnum, Int32> data = new Dictionary<TestEnum, Int32>();

data.Add(TestEnum.A, 1);
data.Add(TestEnum.B, 2);
data.Add(TestEnum.C, 3);

JavaScriptSerializer serializer = new JavaScriptSerializer();
Dictionary<string, Int32> dataToSerialize = data.Keys.ToDictionary(p => p.ToString(), p => data[p]);
string dataSerialized = serializer.Serialize(dataToSerialize);