NewtonSoft Json Serialize and Deserialize class with property of type IEnumerable ISomeInterface

Question

I am trying to move some code to consume ASP NET MVC Web API generated Json data instead of SOAP Xml   I have run into a problem with serializing and deserializing properties of type   IEnumerable lt ISomeInterface gt     Here is a simple example   public interface ISample    int SampleId   get  set      public class Sample   ISample    public int SampleId   get  set      public class SampleGroup    public int GroupId   get  set      public IEnumerable lt ISample gt  Samples   get  set           I can serialize instances of SampleGroup easily with   var sz   JsonConvert SerializeObject  sampleGroupInstance      However the corresponding deserialize fails   JsonConvert DeserializeObject lt SampleGroup gt   sz      with this exception message    Could not create an instance of type JsonSerializationExample ISample  Type is an interface or abstract class and cannot be instantated    If I derive a JsonConverter I can decorate my property as follows    JsonConverter  typeof  SamplesJsonConverter     public IEnumerable lt ISample gt  Samples   get  set      Here is the JsonConverter    public class SamplesJsonConverter   JsonConverter    public override bool CanConvert  Type objectType        return   objectType    typeof  IEnumerable lt ISample gt             public override object ReadJson  JsonReader reader  Type objectType  object existingValue  JsonSerializer serializer        var jA   JArray Load  reader        return jA Select  jl   gt  serializer Deserialize lt Sample gt   new JTokenReader  jl       Cast lt ISample gt     ToList            public override void WriteJson  JsonWriter writer  object value  JsonSerializer serializer            What works here          This converter solves the deserialization problem but I cannot figure how to code the WriteJson method to get serialization working again   Can anybody assist     Is this a  correct  way to solve the problem in the first place

User · Answer

I solved that problem by using a special setting for JsonSerializerSettings which is called TypeNameHandling.All

TypeNameHandling setting includes type information when serializing JSON and read type information so that the create types are created when deserializing JSON

Serialization:

var settings = new JsonSerializerSettings { TypeNameHandling = TypeNameHandling.All };
var text = JsonConvert.SerializeObject(configuration, settings);

Deserialization:

var settings = new JsonSerializerSettings { TypeNameHandling = TypeNameHandling.All };
var configuration = JsonConvert.DeserializeObject<YourClass>(json, settings);

The class YourClass might have any kind of base type fields and it will be serialized properly.

User · Answer

You don t need to use JsonConverterAttribute  keep your model clean  also use CustomCreationConverter  the code is simpler   public class SampleConverter   CustomCreationConverter lt ISample gt        public override ISample Create Type objectType                return new Sample              Then   var sz   JsonConvert SerializeObject  sampleGroupInstance    JsonConvert DeserializeObject lt SampleGroup gt   sz  new SampleConverter       Documentation  Deserialize with CustomCreationConverter

User · Answer

Having that   public interface ITerm       string Name   get       public class Value   ITerm     public class Variable   ITerm     public class Query      public IList lt ITerm gt  Terms   get            I managed conversion trick implementing that   public class TermConverter   JsonConverter       public override void WriteJson JsonWriter writer  object value  JsonSerializer serializer                var field   value GetType   Name          writer WriteStartObject            writer WritePropertyName field           writer WriteValue  value as ITerm   Name           writer WriteEndObject               public override object ReadJson JsonReader reader  Type objectType  object existingValue          JsonSerializer serializer                var jsonObject   JObject Load reader           var properties   jsonObject Properties   ToList            var value    string  properties 0  Value          return properties 0  Name Equals  Value      ITerm  new Value value    new Variable value              public override bool CanConvert Type objectType                return typeof  ITerm     objectType    typeof  Value     objectType    typeof  Variable     objectType            It allows me to serialize and deserialize in JSON like    string JsonQuery       Terms       Value     This is        Variable     X       Value                  var query   new Query new Value  This is     new Variable  X    new Value        var serializeObject   JsonConvert SerializeObject query  new TermConverter     Assert AreEqual JsonQuery  serializeObject       var queryDeserialized   JsonConvert DeserializeObject lt Query gt  JsonQuery  new TermConverter

User · Answer

In my projects  this piece of code always worked as a default serializer which serializes the specified value as if there was no special converter   serializer Serialize writer  value

User · Answer

It is quite simple and out of the box support provided by json net  you just have to use the following JsonSettings while serializing and Deserializing   JsonConvert SerializeObject graph Formatting None  new JsonSerializerSettings         TypeNameHandling  TypeNameHandling Objects      TypeNameAssemblyFormat   System Runtime Serialization Formatters FormatterAssemblyStyle Simple       and for Deserialzing use the below code    JsonConvert DeserializeObject Encoding UTF8 GetString bData  type      new JsonSerializerSettings   TypeNameHandling   TypeNameHandling Objects       Just take a note of the JsonSerializerSettings object initializer  that is important for you

User · Answer

Considering that in most cases you don t want your entire data contract to have types supplied  but only those which are containing an abstract or interface  or list thereof  and also considering these instances are very rare and easily identifiable within your data entities  the easiest and least verbose way is to use  JsonProperty ItemTypeNameHandling   TypeNameHandling Objects   public IEnumerable lt ISomeInterface gt  Items   get  set     as attribute on your property containing the enumerable list collection  This will target only that list  and only append type information for the contained objects  like this       quot Items quot                  quot  type quot    quot Namespace ClassA  Assembly quot          quot Property quot    quot Value quot                      quot  type quot    quot Namespace ClassB  Assembly quot          quot Property quot    quot Value quot          quot Additional ClassB Property quot   3              Clean  simple  and located where the complexity of your data model is introduced  instead of hidden away in some converter

User · Answer

Great solution  thank you  I took the AndyDBell s question and Cuong Le s answer to build an example with two diferent interface s implementation   public interface ISample       int SampleId   get  set       public class Sample1   ISample       public int SampleId   get  set        public Sample1           public class Sample2   ISample       public int SampleId   get  set        public String SampleName   get  set        public Sample2          public class SampleGroup       public int GroupId   get  set        public IEnumerable lt ISample gt  Samples   get  set       class Program       static void Main string   args                  Sample1 instance         var sz       GroupId   1   Samples       SampleId   1     SampleId   2              var j   JsonConvert DeserializeObject lt SampleGroup gt  sz  new SampleConverter lt Sample1 gt              foreach  var item in j Samples                        Console WriteLine  id  0    item SampleId                       Sample2 instance         var sz2       GroupId   1   Samples       SampleId   1    SampleName     Test1       SampleId   2    SampleName     Test2                var j2   JsonConvert DeserializeObject lt SampleGroup gt  sz2  new SampleConverter lt Sample2 gt                Print to show that the unboxing to Sample2 preserved the SampleName s values         foreach  var item in j2 Samples                        Console WriteLine  id  0  name  1    item SampleId   item as Sample2  SampleName                     Console ReadKey              And a generic version to the SampleConverter   public class SampleConverter lt T gt    CustomCreationConverter lt ISample gt  where T  new          public override ISample Create Type objectType                return   ISample new T

User · Answer

I got this to work   explicit conversion      public override object ReadJson JsonReader reader  Type objectType  object existingValue                                      JsonSerializer serializer                var jsonObj   serializer Deserialize lt List lt SomeObject gt  gt  reader           var conversion   jsonObj ConvertAll  x    gt  x as ISomeObject            return conversion

[c#] NewtonSoft.Json Serialize and Deserialize class with property of type IEnumerable<ISomeInterface>

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