Convert from json to Enum with Newtonsoft C#

Question

How could i deserialize json into a List of enum in C#?

I wrote the following code:

 //json "types" : [ "hotel", "spa" ] public enum eType { [Description("hotel")] kHotel, [Description("spa")] kSpa } public class HType { List<eType> m_types; [JsonProperty("types")] public List<eType> HTypes { get { return m_types; } set { // i did this to try and decide in the setter // what enum value should be for each type // making use of the Description attribute // but throws an exception }

} }

 //other class var hTypes = JsonConvert.DeserializeObject<HType>(json);

What exactly is your problem? Deserializing an HType object would also deserialize its members, including the HTypes list. If it doesn't in your case, post an example JSON file with a serialized HType object, please. — user2819245
– user2819245, Commented Oct 20, 2013 at 18:24
It doesn't deserialize to Enum, it doesn't know how to do that. My question is how to deserialize the json from example to enum entries. — Dan Dinu
– Dan Dinu, Commented Oct 20, 2013 at 18:38

L.B · Accepted Answer · 2013-10-20 19:42:07Z

A custom converter may help.

var hType = JsonConvert.DeserializeObject<HType>( @"{""types"" : [ ""hotel"", ""spa"" ]}", new MyEnumConverter());

public class HType { public List<eType> types { set; get; } } public enum eType { [Description("hotel")] kHotel, [Description("spa")] kSpa } public class MyEnumConverter : JsonConverter { public override bool CanConvert(Type objectType) { return objectType == typeof(eType); } public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) { var eTypeVal = typeof(eType).GetMembers() .Where(x => x.GetCustomAttributes(typeof(DescriptionAttribute)).Any()) .FirstOrDefault(x => ((DescriptionAttribute)x.GetCustomAttribute(typeof(DescriptionAttribute))).Description == (string)reader.Value); if (eTypeVal == null) return Enum.Parse(typeof(eType), (string)reader.Value); return Enum.Parse(typeof(eType), eTypeVal.Name); } public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) { throw new NotImplementedException(); } }

While older Json.NET versions suffered from an incomplete (or buggy) StringEnumConverter, this issue has been fixed since roughly a year or so (iirc). Nowadays, you just need to add Json.NET's StringEnumConverter to the serializer settings, and Bob's your uncle...
@elgonzo I knew someone would comment this :) Just try and see that it will not work. If you are sure, post it as answer with working code.
Yes, it does. I use it, including the StringEnumConverter to deserialize enum strings -- this even works with flag-enums. :-) Which Json.NET version are you using? I am using Json.NET 5.0.6.16206 (the DLL for .NET 4.0).
@elgonzo Then post it as answer. (BTW: I just got the latest version of Json.Net from Nuget).
L.B: Holy cow, you got me there :) I totally missed the part regarding the [Description] attribute. You are right. I was the whole time fixated on the enum value names. Now i feel embarrassed... ;)

Brian Rice · Accepted Answer · 2019-03-31 14:10:18Z

Here is my version of an enum converter for ANY enum type... it will handle either a numeric value or a string value for the incoming value. As well as nullable vs non-nullable results.

public class MyEnumConverter : JsonConverter { public override bool CanConvert(Type objectType) { if (!objectType.IsEnum) { var underlyingType = Nullable.GetUnderlyingType(objectType); if (underlyingType != null && underlyingType.IsEnum) objectType = underlyingType; } return objectType.IsEnum; } public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) { if (!objectType.IsEnum) { var underlyingType = Nullable.GetUnderlyingType(objectType); if (underlyingType != null && underlyingType.IsEnum) objectType = underlyingType; } var value = reader.Value; string strValue; if (value == null || string.IsNullOrWhiteSpace(value.ToString())) { if (existingValue == null || Nullable.GetUnderlyingType(existingValue.GetType()) != null) return null; strValue = "0"; } else strValue = value.ToString(); int intValue; if (int.TryParse(strValue, out intValue)) return Enum.ToObject(objectType, intValue); return Enum.Parse(objectType, strValue); } public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) { throw new NotImplementedException(); } }

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