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How to deserialize an abstract class? [duplicate]

I am trying to deserialize a JSON string to a concrete class, which inherits from an abstract class, but I just can't get it working. I have googled and tried some solutions but they don't seem to work either.
This is what I have now:
abstract class AbstractClass { }
class ConcreteClass { }
public AbstractClass Decode(string jsonString)
{
JsonSerializerSettings jss = new JsonSerializerSettings();
jss.TypeNameHandling = TypeNameHandling.All;
return (AbstractClass)JsonConvert.DeserializeObject(jsonString, null, jss);
}
However, if I try to cast the resulting object, it just doesn't work.
The reason why I don't use DeserializeObject is that I have many concrete classes.
Any suggestions?
I am using Newtonsoft.Json

One may not want to use TypeNameHandling (because one wants more compact json or wants to use a specific name for the type variable other than "$type"). Meanwhile, the customCreationConverter approach will not work if one wants to deserialize the base class into any of multiple derived classes without knowing which one to use in advance.
An alternative is to use an int or other type in the base class and define a JsonConverter.
[JsonConverter(typeof(BaseConverter))]
abstract class Base
{
public int ObjType { get; set; }
public int Id { get; set; }
}
class DerivedType1 : Base
{
public string Foo { get; set; }
}
class DerivedType2 : Base
{
public string Bar { get; set; }
}
The JsonConverter for the base class can then deserialize the object based on its type. The complication is that to avoid a stack overflow (where the JsonConverter repeatedly calls itself), a custom contract resolver must be used during this deserialization.
public class BaseSpecifiedConcreteClassConverter : DefaultContractResolver
{
protected override JsonConverter ResolveContractConverter(Type objectType)
{
if (typeof(Base).IsAssignableFrom(objectType) && !objectType.IsAbstract)
return null; // pretend TableSortRuleConvert is not specified (thus avoiding a stack overflow)
return base.ResolveContractConverter(objectType);
}
}
public class BaseConverter : JsonConverter
{
static JsonSerializerSettings SpecifiedSubclassConversion = new JsonSerializerSettings() { ContractResolver = new BaseSpecifiedConcreteClassConverter() };
public override bool CanConvert(Type objectType)
{
return (objectType == typeof(Base));
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
JObject jo = JObject.Load(reader);
switch (jo["ObjType"].Value<int>())
{
case 1:
return JsonConvert.DeserializeObject<DerivedType1>(jo.ToString(), SpecifiedSubclassConversion);
case 2:
return JsonConvert.DeserializeObject<DerivedType2>(jo.ToString(), SpecifiedSubclassConversion);
default:
throw new Exception();
}
throw new NotImplementedException();
}
public override bool CanWrite
{
get { return false; }
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
throw new NotImplementedException(); // won't be called because CanWrite returns false
}
}
That's it. Now you can use serialize/deserialize any derived class. You can also use the base class in other classes and serialize/deserialize those without any additional work:
class Holder
{
public List<Base> Objects { get; set; }
}
string json = #"
[
{
""Objects"" :
[
{ ""ObjType"": 1, ""Id"" : 1, ""Foo"" : ""One"" },
{ ""ObjType"": 1, ""Id"" : 2, ""Foo"" : ""Two"" },
]
},
{
""Objects"" :
[
{ ""ObjType"": 2, ""Id"" : 3, ""Bar"" : ""Three"" },
{ ""ObjType"": 2, ""Id"" : 4, ""Bar"" : ""Four"" },
]
},
]";
List<Holder> list = JsonConvert.DeserializeObject<List<Holder>>(json);
string serializedAgain = JsonConvert.SerializeObject(list);
Debug.WriteLine(serializedAgain);

I would suggest to use CustomCreationConverter in the following way:
public enum ClassDiscriminatorEnum
{
ChildClass1,
ChildClass2
}
public abstract class BaseClass
{
public abstract ClassDiscriminatorEnum Type { get; }
}
public class Child1 : BaseClass
{
public override ClassDiscriminatorEnum Type => ClassDiscriminatorEnum.ChildClass1;
public int ExtraProperty1 { get; set; }
}
public class Child2 : BaseClass
{
public override ClassDiscriminatorEnum Type => ClassDiscriminatorEnum.ChildClass2;
}
public class BaseClassConverter : CustomCreationConverter<BaseClass>
{
private ClassDiscriminatorEnum _currentObjectType;
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
var jobj = JObject.ReadFrom(reader);
_currentObjectType = jobj["Type"].ToObject<ClassDiscriminatorEnum>();
return base.ReadJson(jobj.CreateReader(), objectType, existingValue, serializer);
}
public override BaseClass Create(Type objectType)
{
switch (_currentObjectType)
{
case ClassDiscriminatorEnum.ChildClass1:
return new Child1();
case ClassDiscriminatorEnum.ChildClass2:
return new Child2();
default:
throw new NotImplementedException();
}
}
}

try something like this
public AbstractClass Decode(string jsonString)
{
var jss = new JavaScriptSerializer();
return jss.Deserialize<ConcreteClass>(jsonString);
}
UPDATE
for this scenario methinks all work as you want
public abstract class Base
{
public abstract int GetInt();
}
public class Der:Base
{
int g = 5;
public override int GetInt()
{
return g+2;
}
}
public class Der2 : Base
{
int i = 10;
public override int GetInt()
{
return i+17;
}
}
....
var jset = new JsonSerializerSettings() { TypeNameHandling = TypeNameHandling.All };
Base b = new Der()
string json = JsonConvert.SerializeObject(b, jset);
....
Base c = (Base)JsonConvert.DeserializeObject(json, jset);
where c type is test.Base {test.Der}
UPDATE
#Gusman suggest use TypeNameHandling.Objects instead of TypeNameHandling.All. It is enough and it will produce a less verbose serialization.

Actually, as it has been stated in an update, the simplest way (in 2019) is to use a simple custom pre-defined JsonSerializerSettings, as explained here
string jsonTypeNameAll = JsonConvert.SerializeObject(priceModels, Formatting.Indented,new JsonSerializerSettings
{
TypeNameHandling = TypeNameHandling.All
});
And for deserializing :
TDSPriceModels models = JsonConvert.DeserializeObject<TDSPriceModels>(File.ReadAllText(jsonPath), new JsonSerializerSettings
{
TypeNameHandling = TypeNameHandling.All
});

public class CustomConverter : JsonConverter
{
private static readonly JsonSerializer Serializer = new JsonSerializer();
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
var jObject = JObject.Load(reader);
var typeString = jObject.Value<string>("Kind"); //Kind is a property in json , from which we know type of child classes
var requiredType = RecoverType(typeString);
return Serializer.Deserialize(jObject.CreateReader(), requiredType);
}
private Type RecoverType(string typeString)
{
if (typeString.Equals(type of child class1, StringComparison.OrdinalIgnoreCase))
return typeof(childclass1);
if (typeString.Equals(type of child class2, StringComparison.OrdinalIgnoreCase))
return typeof(childclass2);
throw new ArgumentException("Unrecognized type");
}
public override bool CanConvert(Type objectType)
{
return typeof(Base class).IsAssignableFrom(objectType) || typeof((Base class) == objectType;
}
public override bool CanWrite { get { return false; } }
}
Now add this converter in JsonSerializerSettings as below
var jsonSerializerSettings = new JsonSerializerSettings();
jsonSerializerSettings.Converters.Add(new Newtonsoft.Json.Converters.StringEnumConverter());
jsonSerializerSettings.Converters.Add(new CustomConverter());
After adding serialize or deserialize base class object as below
JsonConvert.DeserializeObject<Type>("json string", jsonSerializerSettings );

I had a similar issue, and I solved it with another way, maybe this would help someone:
I have json that contains in it several fields that are always the same, except for one field called "data" that can be a different type of class every time.
I would like to de-serialize it without analayzing every filed specific.
My solution is:
To define the main class (with 'Data' field) with , the field Data is type T.
Whenever that I de-serialize, I specify the type:
MainClass:
public class MainClass<T>
{
[JsonProperty("status")]
public Statuses Status { get; set; }
[JsonProperty("description")]
public string Description { get; set; }
[JsonProperty("data")]
public T Data { get; set; }
public static MainClass<T> Parse(string mainClsTxt)
{
var response = JsonConvert.DeserializeObject<MainClass<T>>(mainClsTxt);
return response;
}
}
User
public class User
{
[JsonProperty("id")]
public int UserId { get; set; }
[JsonProperty("first_name")]
public string FirstName { get; set; }
[JsonProperty("last_name")]
public string LastName { get; set; }
}
Product
public class Product
{
[JsonProperty("product_id")]
public int ProductId { get; set; }
[JsonProperty("product_name")]
public string ProductName { get; set; }
[JsonProperty("stock")]
public int Stock { get; set; }
}
Using
var v = MainClass<User>.Parse(userJson);
var v2 = MainClass<Product>.Parse(productJson);
json example
userJson: "{"status":1,"description":"my description","data":{"id":12161347,"first_name":"my fname","last_name":"my lname"}}"
productJson: "{"status":1,"description":"my description","data":{"product_id":5,"product_name":"my product","stock":1000}}"

public abstract class JsonCreationConverter<T> : JsonConverter
{
protected abstract T Create(Type objectType, JObject jObject);
public override bool CanConvert(Type objectType)
{
return typeof(T) == objectType;
}
public override object ReadJson(JsonReader reader,Type objectType,
object existingValue, JsonSerializer serializer)
{
try
{
var jObject = JObject.Load(reader);
var target = Create(objectType, jObject);
serializer.Populate(jObject.CreateReader(), target);
return target;
}
catch (JsonReaderException)
{
return null;
}
}
public override void WriteJson(JsonWriter writer, object value,
JsonSerializer serializer)
{
throw new NotImplementedException();
}
}
Now implement this interface
public class SportActivityConverter : JsonCreationConverter<BaseSportActivity>
{
protected override BaseSportActivity Create(Type objectType, JObject jObject)
{
BaseSportActivity result = null;
try
{
switch ((ESportActivityType)jObject["activityType"].Value<int>())
{
case ESportActivityType.Football:
result = jObject.ToObject<FootballActivity>();
break;
case ESportActivityType.Basketball:
result = jObject.ToObject<BasketballActivity>();
break;
}
}
catch(Exception ex)
{
Debug.WriteLine(ex);
}
return result;
}
}

How to define string to object/dictionary in JSON

I create a class for define my request, I don't get the accepted JSON string
I define this object:
public class Request
{
public Var_Args[] var_args { get; set; }
}
public class Var_Args
{
public object title { get; set; }
public object owner { get; set; }
}
when I convert it to json, I get the following string:
{"requests":[{"var_args":[{"title":"Test","owner":"skaner"}]}]}
how can I define the class, for get the accepted json string:
{"requests":[{"var_args":[{"title":"Test"},{"owner":"skaner"}]}]}

You can write a custom JSON converter that can serialize every property of an object (of a known type) into a different JSON object.
public class PropertyAsObjectConverter : JsonConverter
{
private readonly Type[] _types;
public PropertyAsObjectConverter(params Type[] types)
{
_types = types;
}
public override bool CanConvert(Type objectType)
{
return _types.Any(t => t == objectType);
}
public override bool CanRead
{
get { return false; }
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
throw new NotImplementedException();
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
var properties = value.GetType().GetProperties(BindingFlags.Public|BindingFlags.Instance);
foreach(var property in properties)
{
var name = property.Name;
var attrs = property.GetCustomAttributes(typeof(JsonPropertyAttribute));
if(attrs != null)
{
if (attrs.FirstOrDefault() is JsonPropertyAttribute attr)
name = attr.PropertyName;
}
writer.WriteStartObject();
writer.WritePropertyName(name);
serializer.Serialize(writer, property.GetValue(value));
writer.WriteEndObject();
}
}
}
This implements only the serialization, but you can extend it to support deserialization too. You can also extend it to serialize fields should you need that.
You can then define your classes as follows. Notice that I am using JsonPropertyAttribute here to specify the name in the serialized JSON.
public class Content
{
[JsonProperty("requests")]
public Request Value { get; set; }
}
public class Request
{
[JsonProperty("var_args")]
public VarArgs[] Arguments { get; set; }
}
public class VarArgs
{
[JsonProperty("title")]
public object Title { get; set; }
[JsonProperty("owner")]
public object Owner { get; set; }
}
This is how you can use it:
static void Main(string[] args)
{
var request = new Content()
{
Value = new Request()
{
Arguments = new VarArgs[]
{
new VarArgs()
{
Title = "Test",
Owner = "Skaner",
}
}
}
};
var text = JsonConvert.SerializeObject(
request,
Formatting.None,
new PropertyAsObjectConverter(typeof(VarArgs)));
Console.WriteLine(text);
}
The output for this sample is the one you expect:
{"requests":{"var_args":[{"title":"Test"},{"owner":"Skaner"}]}}

You could use a custom JsonConverter like the below.
It takes the Var_Args object and splits it in two different JObject which correspond to two different JSON objects.
public class VarArgsConverter : JsonConverter
{
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
var obj = (JObject)JToken.FromObject(value);
var objTitle = new JObject();
objTitle.Add("title", obj.GetValue("title"));
var objOwner = new JObject();
objOwner.Add("owner", obj.GetValue("owner"));
objTitle.WriteTo(writer);
objOwner.WriteTo(writer);
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
throw new NotImplementedException("Unnecessary because CanRead is false. The type will skip the converter.");
}
public override bool CanRead
{
get { return false; }
}
public override bool CanConvert(Type objectType)
{
return objectType == typeof(Var_Args);
}
}
public class Wrapper
{
[JsonProperty("requests")]
public Request Requests { get; set; }
}
public class Request
{
public Var_Args[] var_args { get; set; }
}
public class Var_Args
{
public object title { get; set; }
public object owner { get; set; }
}
Then use it:
var wrapper = new Wrapper();
var request = new Request();
request.var_args = new Var_Args[] {
new Var_Args(){ title = "Test", owner = "skaner" },
new Var_Args(){ title = "Test2", owner = "skaner2" }
};
wrapper.Requests = request;
var serialized = JsonConvert.SerializeObject(wrapper, new VarArgsConverter());
Output
{"requests":{"var_args":[{"title":"Test"},{"owner":"skaner"},{"title":"Test2"},{"owner":"skaner2"}]}}
Note: I'm using the Wrapper class just to produce the requested JSON.
If you don't want to specify the converter each time, you can register your converter globally. Please see this answer which explains how you can do that. So, the serializer will use your custom JsonConverter every time you try to serialize a Var_Args object.
If you register the JsonConvert globally you can use:
var serialized = JsonConvert.SerializeObject(wrapper);

You can use System.Reflection to redefine Var_Args as an implementation of the IEnumerable<Dictionary<string,object>> interface by adding two methods to the class:
public class Var_Args : IEnumerable<Dictionary<string,object>>
{
IEnumerator IEnumerable.GetEnumerator()
{
return this.GetEnumerator();
}
public IEnumerator<Dictionary<string,object>> GetEnumerator()
{
var Properties = GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance);
foreach (var Property in Properties)
{
var Entry = new Dictionary<string,object>();
Entry.Add(Property.Name, Property.GetValue(this));
yield return Entry;
}
}
public object title { get; set; }
public object owner { get; set; }
}
While Reflection may be regarded as slow, there is a technique you can use to statically compile an IEnumerable at runtime so that the reflection only occurs once for the definition of the class, like this:
public class Var_Args : IEnumerable<Dictionary<string,object>>
{
private struct PropertyList<T>
{
public static readonly List<Func<T,Dictionary<string,object>>> PropertyGetters;
static PropertyList()
{
PropertyGetters = new List<Func<T,Dictionary<string,object>>>();
var Properties = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);
foreach (var Property in Properties)
{
var Args = new [] { Expression.Parameter(typeof(T)) };
var Key = Property.Name;
var Value = Expression.Property(Args[0], Property);
Func<T,object> Get = Expression.Lambda<Func<T,object>>(Value, Args).Compile();
PropertyGetters.Add(obj =>
{
var entry = new Dictionary<string,object>();
entry.Add(Key, Get(obj));
return entry;
});
}
}
}
protected static IEnumerable<Dictionary<string,object>> GetPropertiesAsEntries<T>(T obj)
{
return PropertyList<T>.PropertyGetters.Select(f => f(obj));
}
IEnumerator IEnumerable.GetEnumerator()
{
return this.GetEnumerator();
}
public IEnumerator<Dictionary<string,object>> GetEnumerator()
{
return GetPropertiesAsEntries(this).GetEnumerator();
}
public object title { get; set; }
public object owner { get; set; }
}

Newtonsoft deserialize multiple JSON files with cross references

I have two JSON files (that I can't change the format for) in the following format:
Main file -
[
{
"Name":"XYZ",
"UnitReferenceId":1
},
{
"Name":"ABC",
"UnitReferenceId":2
}
]
The lookup/reference JSON file -
[
{
"UnitReferenceId":1,
"Units":[
{
"Unit":"mg",
"Scale":1
},
{
"Unit":"gm",
"Scale":1000
},
{
"Unit":"kg",
"Scale":1000000
}
]
},
{
"UnitReferenceId":2,
"Units":[
{
"Unit":"mm",
"Scale":1
},
{
"Unit":"m",
"Scale":1000
},
{
"Unit":"km",
"Scale":1000000
}
]
}
]
How would I go about deserializing that into C# classes using Newtonsoft JSON into something like:
public class Widget
{
public string Name {get; set;}
public UnitReference UnitReference { get; set; }
}
public class UnitReference
{
public long UnitReferenceId { get; set; }
public List<Unit> Units { get; set; }
}
public class Unit
{
[JsonProperty("Unit")]
public string UnitValue { get; set; }
public long Scale { get; set; }
}
Any help would be greatly appreciated!

You can do this by reading your two JSON files as follows:
First read the lookup/reference JSON file for UnitReference as a List<UnitReference>, then convert to a Dictionary<long, UnitReference> lookup table.
Next, read the main file using a custom JsonConverter for Widget that is passed the Dictionary<long, UnitReference> lookup table and can translate between UnitReferenceId and UnitReference during reading and writing.
Thus your classes would look like the following:
public class UnitReference
{
readonly long unitReferenceId;
public UnitReference(long unitReferenceId)
{
this.unitReferenceId = unitReferenceId;
}
public long UnitReferenceId { get { return unitReferenceId; } }
public List<Unit> Units { get; set; }
}
public class Unit
{
[JsonProperty("Unit")]
public string UnitValue { get; set; }
public long Scale { get; set; }
}
public class Widget
{
public string Name { get; set; }
public UnitReference UnitReference { get; set; }
}
(My only modification was to make UnitReferenceId be read-only so that it safely could be used as a dictionary key.)
Then, define the following converter:
public class WidgetConverter : CustomPropertyConverterBase<Widget>
{
readonly IDictionary<long, UnitReference> units;
public WidgetConverter(IDictionary<long, UnitReference> units)
{
this.units = units;
}
protected override void ReadCustomProperties(JObject obj, Widget value, JsonSerializer serializer)
{
var id = (long?)obj.GetValue("UnitReferenceId", StringComparison.OrdinalIgnoreCase);
if (id != null)
value.UnitReference = units[id.Value];
}
protected override bool ShouldSerialize(JsonProperty property, object value)
{
if (property.UnderlyingName == nameof(Widget.UnitReference))
return false;
return base.ShouldSerialize(property, value);
}
protected override void WriteCustomProperties(JsonWriter writer, Widget value, JsonSerializer serializer)
{
if (value.UnitReference != null)
{
writer.WritePropertyName("UnitReferenceId");
writer.WriteValue(value.UnitReference.UnitReferenceId);
}
}
}
public abstract class CustomPropertyConverterBase<T> : JsonConverter where T : class
{
public override bool CanConvert(Type objectType)
{
return typeof(T).IsAssignableFrom(objectType);
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
if (reader.TokenType == JsonToken.Null)
return null;
var jObj = JObject.Load(reader);
var contract = (JsonObjectContract)serializer.ContractResolver.ResolveContract(objectType);
var value = existingValue as T ?? (T)contract.DefaultCreator();
ReadCustomProperties(jObj, value, serializer);
// Populate the remaining properties.
using (var subReader = jObj.CreateReader())
{
serializer.Populate(subReader, value);
}
return value;
}
protected abstract void ReadCustomProperties(JObject obj, T value, JsonSerializer serializer);
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
var contract = (JsonObjectContract)serializer.ContractResolver.ResolveContract(value.GetType());
writer.WriteStartObject();
foreach (var property in contract.Properties.Where(p => ShouldSerialize(p, value)))
{
var propertyValue = property.ValueProvider.GetValue(value);
if (propertyValue == null && serializer.NullValueHandling == NullValueHandling.Ignore)
continue;
writer.WritePropertyName(property.PropertyName);
serializer.Serialize(writer, propertyValue);
}
WriteCustomProperties(writer, (T)value, serializer);
writer.WriteEndObject();
}
protected virtual bool ShouldSerialize(JsonProperty property, object value)
{
return property.Readable && !property.Ignored && (property.ShouldSerialize == null || property.ShouldSerialize(value));
}
protected abstract void WriteCustomProperties(JsonWriter writer, T value, JsonSerializer serializer);
}
And deserialize as follows:
var units = JsonConvert.DeserializeObject<List<UnitReference>>(unitsJsonString)
.ToDictionary(u => u.UnitReferenceId);
var settings = new JsonSerializerSettings
{
Converters = { new WidgetConverter(units) },
};
var widgets = JsonConvert.DeserializeObject<List<Widget>>(widgetsJsonString, settings);
Notes:
Here I am deserializing from JSON strings for demo purposes, but you can deserialize directly from your file(s) as shown in Deserialize JSON from a file.
The base class CustomPropertyConverterBase<T> for WidgetConverter automatically reads and writes all properties for the object being (de)serialized. WidgetConverter then overrides this behavior for the UnitReference property only, avoiding the necessity to manually serialize all the remaining properties of Widget.
Sample fiddle.

I use json2csharp for creating my classes quickly. If you have to implement it in code, see JSON C# Class Generator Project.

Map Json to custom class

I have following json:
{"EventMessageUId":"ef51b5a3-32b2-e611-baf9-fc3fdb446bd2","Message":
"{\"StoryId\":20500,\"StoryDesc\":\"Test Story
data\"}","ProjectId":"1"}
Below is the class in which I'm trying to map it:
public class Requirments
{
public int FileID { get; set; }
public string EventMessageUId { get; set; }
public string ProjectId { get; set; }
public List<Message> Message { get; set; }
//public object[] Message { get; set; }
public string error { get; set; }
}
It is taking message tag as a string
"Message": "{\"StoryId\":20500,\"StoryDesc\":\"Test Story data\"}"
I want to Map it into List<Message>
public class Message
{
public string StoryID { get; set; }
public string StoryDesc { get; set; }
}
What can I do for this without changing json?
In the current scenario it gives me an error when I try it with List<Message>

This might do the trick for you
string jsonstr = File.ReadAllText(YourJSONFile);
jsonstr = jsonstr.Replace("\"{", "{");
jsonstr = jsonstr.Replace("}\"", "}");
jsonstr = jsonstr.Replace("\\", "");
var ser = JsonConvert.DeserializeObject<MyMessages>(jsonstr);
The classes would look like
public class Message
{
[JsonProperty("StoryId")]
public int StoryId { get; set; }
[JsonProperty("StoryDesc")]
public string StoryDesc { get; set; }
}
public class MyMessages
{
[JsonProperty("Message")]
public Message Message { get; set; }
}
The problem with the JSON is
"Message": "{\"StoryId\":20500,\"StoryDesc\":\"Test Story data\"}"
^ ^
are these " which is making it a string instead of two different properties of JSON. So we removed that "{ and }" with
jsonstr = jsonstr.Replace("\"{", "{");
jsonstr = jsonstr.Replace("}\"", "}");
and now the remaining JSON string will be
"Message": {\"StoryId\":20500,\"StoryDesc\":\"Test Story data\"}
^ ^ ^ ^ ^ ^
in which we have \ back slash in the JSON string which will again creates issue while deseralizing the JSON string. So
jsonstr = jsonstr.Replace("\\", "");

You have two different problems in deserializing your JSON to your Requirments class:
The Message property contains nested double-serialized data. I.e. the sending system serialized the original Message object to a JSON string then included that in an outer container object that was subsequently itself serialized, causing the inner JSON data to be escaped.
The nested JSON represents a single object - a collection of name/value pairs surrounded by braces. But you want to deserialize to a List<Message>, and all JSON serializers will map a List<T> to a JSON array rather than to a JSON object.
Both these problems can be overcome by using json.net combined with a custom JsonConverter for the Message property. However, the conversion will require two independent steps:
You will need to unwrap the nested double-serialized JSON into a string.
And then map the JSON object thereby unwrapped with a converter similar to SingleOrArrayConverter<T> from How to handle both a single item and an array for the same property using JSON.net.
The following set of converters performs this chained conversion:
public class SingleOrArrayConverter<TCollection, TItem> : SingleOrArrayConverter where TCollection : ICollection<TItem>
{
public override bool CanConvert(Type objectType)
{
if (!base.CanConvert(objectType))
return false;
return typeof(TCollection).IsAssignableFrom(objectType);
}
}
public class SingleOrArrayConverter : JsonConverter
{
public override bool CanConvert(Type objectType)
{
if (objectType.IsArray || objectType == typeof(string) || objectType.IsPrimitive)
return false;
Type elementType = null;
foreach (var type in objectType.GetCollectItemTypes())
{
if (elementType == null)
elementType = type;
else
return false;
}
return elementType != null;
}
object ReadJsonGeneric<TItem>(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
if (reader.TokenType == JsonToken.Null)
return null;
var collection = (ICollection<TItem>)(existingValue ?? serializer.ContractResolver.ResolveContract(objectType).DefaultCreator());
if (reader.TokenType == JsonToken.StartArray)
serializer.Populate(reader, collection);
else
collection.Add(serializer.Deserialize<TItem>(reader));
return collection;
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
if (reader.TokenType == JsonToken.Null)
return null;
if (objectType.IsArray)
throw new JsonSerializationException("Read-only collections such as arrays are not supported");
try
{
var elementType = objectType.GetCollectItemTypes().SingleOrDefault();
if (elementType == null)
throw new JsonSerializationException(string.Format("{0} is not an ICollection<T> for some T", objectType));
var method = typeof(SingleOrArrayConverter).GetMethod("ReadJsonGeneric", BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Public);
return method.MakeGenericMethod(new[] { elementType }).Invoke(this, new object[] { reader, objectType, existingValue, serializer });
}
catch (Exception ex)
{
// Wrap the TargetInvocationException in a JsonSerializerException
throw new JsonSerializationException("Failed to deserialize " + objectType, ex);
}
}
void WriteJsonGeneric<TItem>(JsonWriter writer, object value, JsonSerializer serializer)
{
var list = (ICollection<TItem>)value;
if (list.Count == 1)
{
foreach (object item in list)
{
serializer.Serialize(writer, item);
break;
}
}
else
{
writer.WriteStartArray();
foreach (var item in list)
{
serializer.Serialize(writer, item);
}
writer.WriteEndArray();
}
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
var objectType = value.GetType();
try
{
var elementType = objectType.GetCollectItemTypes().SingleOrDefault();
if (elementType == null)
throw new JsonSerializationException(string.Format("{0} is not an ICollection<T> for some T", objectType));
var method = typeof(SingleOrArrayConverter).GetMethod("WriteJsonGeneric", BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Public);
method.MakeGenericMethod(new[] { elementType }).Invoke(this, new object[] { writer, value, serializer });
}
catch (Exception ex)
{
// Wrap the TargetInvocationException in a JsonSerializerException
throw new JsonSerializationException("Failed to serialize " + objectType, ex);
}
}
}
public static class TypeExtensions
{
public static IEnumerable<Type> GetInterfacesAndSelf(this Type type)
{
if (type == null)
throw new ArgumentNullException();
if (type.IsInterface)
return new[] { type }.Concat(type.GetInterfaces());
else
return type.GetInterfaces();
}
public static IEnumerable<Type> GetCollectItemTypes(this Type type)
{
foreach (Type intType in type.GetInterfacesAndSelf())
{
if (intType.IsGenericType
&& intType.GetGenericTypeDefinition() == typeof(ICollection<>))
{
yield return intType.GetGenericArguments()[0];
}
}
}
}
public class StringConverterDecorator : JsonConverterDecorator
{
public StringConverterDecorator(Type jsonConverterType) : base(jsonConverterType) { }
public StringConverterDecorator(JsonConverter converter) : base(converter) { }
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
if (reader.TokenType == JsonToken.Null)
return null;
// Unwrap the double-serialized string.
var s = JToken.Load(reader).ToString();
var token = JToken.Parse(s);
// Then convert the revealed JSON to its final form.
using (var subReader = token.CreateReader())
{
while (subReader.TokenType == JsonToken.None)
subReader.Read();
return base.ReadJson(subReader, objectType, existingValue, serializer);
}
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
string s;
// Serialize the value to an intermediate JSON string.
using (var textWriter = new StringWriter())
{
using (var subWriter = new JsonTextWriter(textWriter))
{
base.WriteJson(subWriter, value, serializer);
}
s = textWriter.ToString();
}
// Then double-serialize the value by writing the JSON as a string literal to the output stream.
writer.WriteValue(s);
}
}
public abstract class JsonConverterDecorator : JsonConverter
{
readonly JsonConverter converter;
public JsonConverterDecorator(Type jsonConverterType) : this((JsonConverter)Activator.CreateInstance(jsonConverterType)) { }
public JsonConverterDecorator(JsonConverter converter)
{
if (converter == null)
throw new ArgumentNullException();
this.converter = converter;
}
public override bool CanConvert(Type objectType)
{
return converter.CanConvert(objectType);
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
return converter.ReadJson(reader, objectType, existingValue, serializer);
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
converter.WriteJson(writer, value, serializer);
}
public override bool CanRead { get { return converter.CanRead; } }
public override bool CanWrite { get { return converter.CanWrite; } }
}
Then apply the chained converter to your Message property using a [JsonConverter(typeof(TConverter), ...)] attribute as follows:
public class Requirments
{
public int FileID { get; set; }
public string EventMessageUId { get; set; }
public string ProjectId { get; set; }
[JsonConverter(typeof(StringConverterDecorator), typeof(SingleOrArrayConverter))]
public List<Message> Message { get; set; }
public string error { get; set; }
}
Then deserialize with JsonConvert.DeserializeObject<T>:
var requirement = JsonConvert.DeserializeObject<Requirments>(jsonString);
Or, if you do not want to apply the converter to directly to your type, you can add it to JsonSerializerSettings.Converters and deserialize as follows:
var settings = new JsonSerializerSettings
{
Converters = { new StringConverterDecorator(new SingleOrArrayConverter<List<Message>, Message>()) },
};
var requirement = JsonConvert.DeserializeObject<Requirments>(json, settings);
Note the generic SingleOrArrayConverter<List<Message>, Message> is required here to prevent the converter from applying to all types of collection.
Sample fiddle.

The definition of the Message class is right. However the Json body for message property is not an array. So the class should be
public class Requirments
{
public int FileID { get; set; }
public string EventMessageUId { get; set; }
public string ProjectId { get; set; }
public Message Message { get; set; }
//public object[] Message { get; set; }
public string error { get; set; }
}

Main problem is with your JSON, it should look like this
{"EventMessageUId":"ef51b5a3-32b2-e611-baf9-fc3fdb446bd2","Message":
[{"StoryId":20500,"StoryDesc":"Test Story
data"}],"ProjectId":"1"}
After that you will get "Message" as a list, and also you can easily map it to class.
public class Message
{
public int StoryId { get; set; }
public string StoryDesc { get; set; }
}
public class Requirments
{
public string EventMessageUId { get; set; }
public List<Message> Message { get; set; }
public string ProjectId { get; set; }
}

I have successfully parsed list of class type Message from your Json but for that you will slightly need to change your class Requirements:
public class Requirments
{
public int FileID { get; set; }
public string EventMessageUId { get; set; }
public string ProjectId { get; set; }
public string Message { get; set; }
//public List<Message> Message { get; set; } // **need to change property type to "string"**
//public object[] Message { get; set; }
public string error { get; set; }
}
You can try below code:
Requirments mainResult = JsonConvert.DeserializeObject<Requirments>("YOUR JSON STING");
List<Message> MessageList = JsonConvert.DeserializeObject<List<Message>>(mainResult.Message.ToString());
Note: you will need to include using Newtonsoft.Json; in your class.
This will give you list of class type Message in MessageList
Hope, this will help!

Json.Net Serialization of Type with Polymorphic Child Object

We would like to be able to serialize/deserialize json from/to C# classes, with the main class having an instance of a polymorphic child object. Doing so is easy using Json.Net's TypeNameHandling.Auto setting. However, we would like to do so without the "$type" field.
The first thought is to be able to rename "$type" to a value of our choosing and to have the value for the type be an enum that would map the sub-types properly. I have not seen that as being an option but would be glad to hear if it is possible.
The second thought was along the following lines... Below is a first pass at classes, with the top level class having an indicator (SubTypeType) as to what type of data is contained in the child object (SubTypeData). I've dug around a bit into the Json.Net documentation and have tried a few things but have had no luck.
We currently have full control over the data definition, but once it is deployed, then things are locked.
public class MainClass
{
public SubType SubTypeType { get; set; }
public SubTypeClassBase SubTypeData { get; set; }
}
public class SubTypeClassBase
{
}
public class SubTypeClass1 : SubTypeClassBase
{
public string AaaField { get; set; }
}
public class SubTypeClass2 : SubTypeClassBase
{
public string ZzzField { get; set; }
}

Having the subtype information in the container class is problematic for two reasons:
The container class instance is not accessible when Json.NET is reading the contained class.
If you later need to convert the SubTypeClassBase property into, say, a list, there will be nowhere to put the subtype information.
Instead, I would recommend adding the subtype information as a property in the base class:
[JsonConverter(typeof(SubTypeClassConverter))]
public class SubTypeClassBase
{
[JsonConverter(typeof(StringEnumConverter))] // Serialize enums by name rather than numerical value
public SubType Type { get { return typeToSubType[GetType()]; } }
}
Now the custom subtype enum will be serialized whenever an object assignable to SubTypeClassBase is serialized. Having done that, for deserialization you can create a JsonConverter that loads the json for a given SubTypeClassBase into a temporary JObject, checks the value of the "Type" property, and deserializes the JSON object as the appropriate class.
Prototype implementation below:
public enum SubType
{
BaseType,
Type1,
Type2,
}
[JsonConverter(typeof(SubTypeClassConverter))]
public class SubTypeClassBase
{
static readonly Dictionary<Type, SubType> typeToSubType;
static readonly Dictionary<SubType, Type> subTypeToType;
static SubTypeClassBase()
{
typeToSubType = new Dictionary<Type,SubType>()
{
{ typeof(SubTypeClassBase), SubType.BaseType },
{ typeof(SubTypeClass1), SubType.Type1 },
{ typeof(SubTypeClass2), SubType.Type2 },
};
subTypeToType = typeToSubType.ToDictionary(pair => pair.Value, pair => pair.Key);
}
public static Type GetType(SubType subType)
{
return subTypeToType[subType];
}
[JsonConverter(typeof(StringEnumConverter))] // Serialize enums by name rather than numerical value
public SubType Type { get { return typeToSubType[GetType()]; } }
}
public class SubTypeClass1 : SubTypeClassBase
{
public string AaaField { get; set; }
}
public class SubTypeClass2 : SubTypeClassBase
{
public string ZzzField { get; set; }
}
public class SubTypeClassConverter : JsonConverter
{
public override bool CanConvert(Type objectType)
{
return objectType == typeof(SubTypeClassBase);
}
public override bool CanWrite { get { return false; } }
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
var token = JToken.Load(reader);
var typeToken = token["Type"];
if (typeToken == null)
throw new InvalidOperationException("invalid object");
var actualType = SubTypeClassBase.GetType(typeToken.ToObject<SubType>(serializer));
if (existingValue == null || existingValue.GetType() != actualType)
{
var contract = serializer.ContractResolver.ResolveContract(actualType);
existingValue = contract.DefaultCreator();
}
using (var subReader = token.CreateReader())
{
// Using "populate" avoids infinite recursion.
serializer.Populate(subReader, existingValue);
}
return existingValue;
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
throw new NotImplementedException();
}
}

You can try with JsonSubtypes converter implementation that support registering type mapping with enum values.
In your case it looks like this:
public class MainClass
{
public SubTypeClassBase SubTypeData { get; set; }
}
[JsonConverter(typeof(JsonSubtypes), "SubTypeType")]
[JsonSubtypes.KnownSubType(typeof(SubTypeClass1), SubType.WithAaaField)]
[JsonSubtypes.KnownSubType(typeof(SubTypeClass2), SubType.WithZzzField)]
public class SubTypeClassBase
{
public SubType SubTypeType { get; set; }
}
public class SubTypeClass1 : SubTypeClassBase
{
public string AaaField { get; set; }
}
public class SubTypeClass2 : SubTypeClassBase
{
public string ZzzField { get; set; }
}
public enum SubType
{
WithAaaField,
WithZzzField
}
[TestMethod]
public void Deserialize()
{
var obj = JsonConvert.DeserializeObject<MainClass>("{\"SubTypeData\":{\"ZzzField\":\"zzz\",\"SubTypeType\":1}}");
Assert.AreEqual("zzz", (obj.SubTypeData as SubTypeClass2)?.ZzzField);
}

Here's a full example that can both read and write JSON with polymorphic objects.
Assuming we have the following class structure:
public class Base {}
public class SubClass1 : Base {
public int field1;
}
public class SubClass2 : Base {
public int field2;
}
We can use a custom converter that creates an extra field in JSON named type when serializing and reads it when deserializing.
public class PolymorphicJsonConverter : JsonConverter
{
public override object ReadJson (JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) {
JObject item = JObject.Load(reader);
var type = item["type"].Value<string>();
if (type == "SubClass1") {
return item.ToObject<SubClass1>();
} else if (type == "SubClass2") {
return item.ToObject<SubClass2>();
} else {
return null;
}
}
public override void WriteJson (JsonWriter writer, object value, JsonSerializer serializer) {
JObject o = JObject.FromObject(value);
if (value is SubClass1) {
o.AddFirst(new JProperty("type", new JValue("SubClass1")));
} else if (value is SubClass1) {
o.AddFirst(new JProperty("type", new JValue("SubClass2")));
}
o.WriteTo(writer);
}
public override bool CanConvert (Type objectType) {
return typeof(Base).IsAssignableFrom(objectType);
}
}
You could use this converter in a container class like so:
public class Container {
public List<Base> items;
public string Save() {
return JsonConvert.SerializeObject(items, new PolymorphicJsonConverter())
}
public void Load(string jsonText) {
items = JsonConvert.DeserializeObject<List<Base>>(jsonText, new PolymorphicJsonConverter());
}
}
Alternatively you could use JSON.net's built in type hinting, instead of rolling your own JsonConverter, but it's not so flexible and creates very un-portable JSON.
JsonConvert.SerializeObject(items, new JsonSerializerSettings {
TypeNameHandling = TypeNameHandling.Auto
});