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DESerialize JSON to c# objects dynamically

I am getting JSON data from a webservice. it is providing me with FORM DATA with different questions and answers. every answer is a different c# object. I am trying to find the best way to map the ANSWERS to correct c# object.
for example if Question Id is "37" Then its a Address Object.
I have JSON String like in this format below
"answers": {
"37": {
"name": "yourAddress37",
"order": "6",
"sublabels": "{\"cc_firstName\":\"First Name\",\"cc_lastName\":\"Last Name\",\"cc_number\":\"Credit Card Number\",\"cc_ccv\":\"Security Code\",\"cc_exp_month\":\"Expiration Month\",\"cc_exp_year\":\"Expiration Year\",\"addr_line1\":\"Street Address\",\"addr_line2\":\"Street Address Line 2\",\"city\":\"City\",\"state\":\"State \\/ Province\",\"postal\":\"Postal \\/ Zip Code\",\"country\":\"Country\"}",
"text": "Your Home Address:",
"type": "control_address",
"answer": {
"addr_line1": "148 east 38st ",
"addr_line2": "",
"city": "Brooklyn ",
"state": "Ny",
"postal": "11203",
"country": ""
},
"prettyFormat": "Street Address: 148 east 38st <br>City: Brooklyn <br>State / Province: Ny<br>Postal / Zip Code: 11203<br>"
},
"38": {
"name": "emergencyContact",
"order": "9",
"sublabels": "{\"prefix\":\"Prefix\",\"first\":\"First Name\",\"middle\":\"Middle Name\",\"last\":\"Last Name\",\"suffix\":\"Suffix\"}",
"text": "Emergency Contact Name:",
"type": "control_fullname",
"answer": {
"first": "Pauline ",
"last": "Sandy "
},
"prettyFormat": "Pauline Sandy "
}
}
and it MAPS to following c# property
public Dictionary<int, answer> answers{ get; set; }
Then I have a generic Answer class
public class answer
{
public string name { get; set; }
public dynamic answer { get; set; }
}
if you look at the ANSWER data from json then you will see its different for every question. for example one answer would be ADDRESS OBJECT, other answer would be FIRST & LAST NAME object.
my question is, how can i deserialize json into correct objects/properties automatically? I can create different POCO objects, such as address & ProfileName, but how would i map them automatically to correct object/property.
EDIT:
Loop through all Answers
foreach (var a in item.answers)
{
// pass the ANSWER OBJECT (dynamic data type) to function
createNewApplication(System.Convert.ToInt16(a.Key), a.Value.answer,ref app);
}
private void createNewApplication(int key, dynamic value,ref HcsApplicant app)
{
if (key == 4) // data is plain string
app.yourPhone = value;
if (key == 8)
app.yourEmail = value;
if (key==37) // data is a object
app.address = value.ToObject<address>();
}
is this approach OK? any cleaner way of doing it?

I personally don't like every option that involves custom parsing and looking directly on the questions.
You can make use of partial deserialization via JToken class.
Just declare your answers dictionary as such:
public Dictionary<int, JToken> Answers{ get; set; }
And then whenever you need the address page you can simply do Answers[37].ToObject<Address>(). How you manage to call this method, depends upon the rest of your code, but you can embed it in properties, in a big switch, in multiple methods, one for each class. One option I like is to have a static From method in each deserializable class:
public class Address
{
public string Name { get; set; }
// all the othe properties
// ....
public static Address From(Dictionary<int, JToken> answers)
{
return answers?.TryGetValue(37, out var address) ?? false
? address?.ToObject<Address>()
: null;
}
}
// so you can just write:
var address = Address.From(answers);
As a side note, remember that the default deserialization settings for Json.Net are case insensitive, so you can deserialize the name property from JSON to a more idiomatic Name property on your POCOs.

Make a constructor for each answer type that constructs by parsing a JSON object string. Make all the answers implement an interface, e.g. IAnswer. Map all constructors (as functions) to the corresponding question IDs in a dictionary. Lastly, loop through the questions, call each constructor, and maybe put them in a new dictionary.
Example code:
interface IAnswer { };
public class ExampleAnswer : IAnswer
{
public ExampleAnswer(String JSONObject)
{
// Parse JSON here
}
}
delegate IAnswer AnswerConstructor(String JSONObject);
Dictionary<int, AnswerConstructor> Constructors = new Dictionary<int, AnswerConstructor>()
{
{1234, ((AnswerConstructor)(json => new ExampleAnswer(json)))}
// Add all answer types here
};
Dictionary<int, IAnswer> ParseAnswers(Dictionary<int, String> JSONObjects)
{
var result = new Dictionary<int, IAnswer>();
foreach (var pair in JSONObjects)
result.Add(pair.Key, Constructors[pair.Key](pair.Value));
return result;
}
Edit: Look at Matt's answer for some good options for how to parse JSON.
Edit2, In response to your edit: That looks like a good way of doing it! I think it's better than my answer, since you can keep all type information, unlike my method.
The only thing I see that you might want to change is using else if or switch instead of multiple ifs. This could increase performance if you have many answers.

You have a couple of options:
Deserialize into a dynamic object using the System.Web package as per this answer or the JSON.Net package as per this answer then use conditional checks/the null propagation operator to access a property.
Automatically deserialize down to the level where there are differences, then have code to manual deserialize the properties that are different into the correct POCO types on your parent Deserialized object.
Leverage one of the Serialization Callbacks provided by JSON.Net (OnDeserializing or OnDeserialized) to handle populating the different properties into the correct types as part of the deserialization pipeline.
With approaches 2 and 3 you could write a nicer helper method on your POCO that inspected the objects properties and returned a result which would be the type that was set (I would recommend returning an Enum) e.g.:
public PropertyTypeEnum GetPropertyType(MyPocoClass myPocoClass)
{
if (myPocoClass.PropertyOne != null)
{
return PropertyTypeEnum.TypeOne;
}
else if (...)
{
return PropertyTypeEnum.TypeN
}
else
{
// probably throw a NotImplementedException here depending on your requirements
}
}
Then in your code to use the object you can use the returned Enum to switch on the logical paths of your code.

ASP.NET Web API 2 and partial updates

We are using ASP.NET Web API 2 and want to expose ability to partially edit some object in the following fashion:
HTTP PATCH /customers/1
{
"firstName": "John",
"lastName": null
}
... to set firstName to "John" and lastName to null.
HTTP PATCH /customers/1
{
"firstName": "John"
}
... in order just to update firstName to "John" and do not touch lastName at all. Suppose we have a lot of properties that we want to update with such semantic.
This is quite convenient behavior that is exercised by OData for instance.
The problem is that default JSON serializer will just come up with null in both cases, so it's impossible to distinguish.
I'm looking for some way to annotate model with some kind of wrappers (with value and flag set/unset inside) that would allow to see this difference. Any existing solutions for this?

I know that answers which are already given cover all aspects already, but just want to share concise summary of what we ended up doing and what seems to work for us pretty well.
Created a generic data contract
[DataContract]
public class RQFieldPatch<T>
{
[DataMember(Name = "value")]
public T Value { get; set; }
}
Created ad-hoc data cotnracts for patch requests
Sample is below.
[DataContract]
public class PatchSomethingRequest
{
[DataMember(Name = "prop1")]
public RQFieldPatch<EnumTypeHere> Prop1 { get; set; }
[DataMember(Name = "prop2")]
public RQFieldPatch<ComplexTypeContractHere> Prop2 { get; set; }
[DataMember(Name = "prop3")]
public RQFieldPatch<string> Prop3 { get; set; }
[DataMember(Name = "prop4")]
public RQFieldPatch<int> Prop4 { get; set; }
[DataMember(Name = "prop5")]
public RQFieldPatch<int?> Prop5 { get; set; }
}
Business Logic
Simple.
if (request.Prop1 != null)
{
// update code for Prop1, the value is stored in request.Prop1.Value
}
Json format
Simple. Not that extensive as "JSON Patch" standard, but covers all our needs.
{
"prop1": null, // will be skipped
// "prop2": null // skipped props also skipped as they will get default (null) value
"prop3": { "value": "test" } // value update requested
}
Properties
Simple contracts, simple logic
No serialization customization
Support for null values assignment
Covers any types: value, reference, complex custom types, whatever

At first I misunderstood the problem. As I was working with Xml I thought it was quite easy. Just add an attribute to the property and leave the property empty. But as I found out, Json doesn't work like that. Since I was looking for a solution that works for both xml and json, you'll find xml references in this answer. Another thing, I wrote this with a C# client in mind.
The first step is to create two classes for serialization.
public class ChangeType
{
[JsonProperty("#text")]
[XmlText]
public string Text { get; set; }
}
public class GenericChangeType<T> : ChangeType
{
}
I've chosen for a generic and a non-generic class because it is hard to cast to a generic type while this is not important. Also, for xml implementation it is necessary that XmlText is string.
XmlText is the actual value of the property. The advantage is that you can add attributes to this object and the fact that this is an object, not just string. In Xml it looks like: <Firstname>John</Firstname>
For Json this doesn't work. Json doesn't know attributes. So for Json this is just a class with properties. To implement the idea of the xml value (I will get to that later), I've renamed the property to #text. This is just a convention.
As XmlText is string (and we want to serialize to string), this is fine to store the value disregard the type. But in case of serialization, I want to know the actual type.
The drawback is that the viewmodel needs to reference these types, the advantage is that the properties are strongly typed for serialization:
public class CustomerViewModel
{
public GenericChangeType<int> Id { get; set; }
public ChangeType Firstname { get; set; }
public ChangeType Lastname { get; set; }
public ChangeType Reference { get; set; }
}
Suppose I set the values:
var customerViewModel = new CustomerViewModel
{
// Where int needs to be saved as string.
Id = new GenericeChangeType<int> { Text = "12" },
Firstname = new ChangeType { Text = "John" },
Lastname = new ChangeType { },
Reference = null // May also be omitted.
}
In xml this will look like:
<CustomerViewModel>
<Id>12</Id>
<Firstname>John</Firstname>
<Lastname />
</CustomerViewModel>
Which is enough for the server to detect the changes. But with json it will generate the following:
{
"id": { "#text": "12" },
"firstname": { "#text": "John" },
"lastname": { "#text": null }
}
It can work, because in my implementation the receiving viewmodel has the same definition. But since you are talking about serialization only and in case you use another implementation you would want:
{
"id": 12,
"firstname": "John",
"lastname": null
}
That is where we need to add a custom json converter to produce this result. The relevant code is in WriteJson, assuming you would add this converter to the serializer settings only. But for the sake of completeness I've added the readJson code as well.
public class ChangeTypeConverter : JsonConverter
{
public override bool CanConvert(Type objectType)
{
// This is important, we can use this converter for ChangeType only
return typeof(ChangeType).IsAssignableFrom(objectType);
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
var value = JToken.Load(reader);
// Types match, it can be deserialized without problems.
if (value.Type == JTokenType.Object)
return JsonConvert.DeserializeObject(value.ToString(), objectType);
// Convert to ChangeType and set the value, if not null:
var t = (ChangeType)Activator.CreateInstance(objectType);
if (value.Type != JTokenType.Null)
t.Text = value.ToString();
return t;
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
var d = value.GetType();
if (typeof(ChangeType).IsAssignableFrom(d))
{
var changeObject = (ChangeType)value;
// e.g. GenericChangeType<int>
if (value.GetType().IsGenericType)
{
try
{
// type - int
var type = value.GetType().GetGenericArguments()[0];
var c = Convert.ChangeType(changeObject.Text, type);
// write the int value
writer.WriteValue(c);
}
catch
{
// Ignore the exception, just write null.
writer.WriteNull();
}
}
else
{
// ChangeType object. Write the inner string (like xmlText value)
writer.WriteValue(changeObject.Text);
}
// Done writing.
return;
}
// Another object that is derived from ChangeType.
// Do not add the current converter here because this will result in a loop.
var s = new JsonSerializer
{
NullValueHandling = serializer.NullValueHandling,
DefaultValueHandling = serializer.DefaultValueHandling,
ContractResolver = serializer.ContractResolver
};
JToken.FromObject(value, s).WriteTo(writer);
}
}
At first I tried to add the converter to the class: [JsonConverter(ChangeTypeConverter)]. But the problem is that the converter will be used at all times, which creates a reference loop (as also mentioned in the comment in the code above). Also you may want to use this converter for serialization only. That is why I've added it to the serializer only:
var serializerSettings = new JsonSerializerSettings
{
NullValueHandling = NullValueHandling.Ignore,
DefaultValueHandling = DefaultValueHandling.IgnoreAndPopulate,
Converters = new List<JsonConverter> { new ChangeTypeConverter() },
ContractResolver = new Newtonsoft.Json.Serialization.CamelCasePropertyNamesContractResolver()
};
var s = JsonConvert.SerializeObject(customerViewModel, serializerSettings);
This will generate the json I was looking for and should be enough to let the server detect the changes.
-- update --
As this answer focusses on serialization, the most important thing is that lastname is part of the serialization string. It then depends on the receiving party how to deserialize the string into an object again.
Serialization and deserialization use different settings. In order to deserialize again you can use:
var deserializerSettings = new JsonSerializerSettings
{
//NullValueHandling = NullValueHandling.Ignore,
DefaultValueHandling = DefaultValueHandling.IgnoreAndPopulate,
Converters = new List<JsonConverter> { new Converters.NoChangeTypeConverter() },
ContractResolver = new Newtonsoft.Json.Serialization.CamelCasePropertyNamesContractResolver()
};
var obj = JsonConvert.DeserializeObject<CustomerViewModel>(s, deserializerSettings);
If you use the same classes for deserialization then Request.Lastname should be of ChangeType, with Text = null.
I'm not sure why removing the NullValueHandling from the deserialization settings causes problems in your case. But you can overcome this by writing an empty object as value instead of null. In the converter the current ReadJson can already handle this. But in WriteJson there has to be a modification. Instead of writer.WriteValue(changeObject.Text); you need something like:
if (changeObject.Text == null)
JToken.FromObject(new ChangeType(), s).WriteTo(writer);
else
writer.WriteValue(changeObject.Text);
This would result in:
{
"id": 12,
"firstname": "John",
"lastname": {}
}

Here's my quick and inexpensive solution...
public static ObjectType Patch<ObjectType>(ObjectType source, JObject document)
where ObjectType : class
{
JsonSerializerSettings settings = new JsonSerializerSettings
{
ContractResolver = new CamelCasePropertyNamesContractResolver()
};
try
{
String currentEntry = JsonConvert.SerializeObject(source, settings);
JObject currentObj = JObject.Parse(currentEntry);
foreach (KeyValuePair<String, JToken> property in document)
{
currentObj[property.Key] = property.Value;
}
String updatedObj = currentObj.ToString();
return JsonConvert.DeserializeObject<ObjectType>(updatedObj);
}
catch (Exception ex)
{
throw ex;
}
}
When fetching the request body from your PATCH based method, make sure to take the argument as a type such as JObject. JObject during iteration returns a KeyValuePair struct which inherently simplifies the modification process. This allows you to get your request body content without receiving a deserialized result of your desired type.
This is beneficial due to the fact that you don't need any additional verification for nullified properties. If you want your values to be nullified that also works because the Patch<ObjectType>() method only loops through properties given in the partial JSON document.
With the Patch<ObjectType>() method, you only need to pass your source or target instance, and the partial JSON document that will update your object. This method will apply camelCase based contract resolver to prevent incompatible and inaccurate property names from being made. This method will then serialize your passed instance of a certain type and turned into a JObject.
The method then replaces all properties from the new JSON document to the current and serialized document without any unnecessary if statements.
The method stringifies the current document which now is modified, and deserializes the modified JSON document to your desired generic type.
If an exception occur, the method will simply throw it. Yes, it is rather unspecific but you are the programmer, you need to know what to expect...
This can all be done on a single and simple syntax with the following:
Entity entity = AtomicModifier.Patch<Entity>(entity, partialDocument);
This is what the operation would normally look like:
// Partial JSON document (originates from controller).
JObject newData = new { role = 9001 };
// Current entity from EF persistence medium.
User user = await context.Users.FindAsync(id);
// Output:
//
// Username : engineer-186f
// Role : 1
//
Debug.WriteLine($"Username : {0}", user.Username);
Debug.WriteLine($"Role : {0}", user.Role);
// Partially updated entity.
user = AtomicModifier.Patch<User>(user, newData);
// Output:
//
// Username : engineer-186f
// Role : 9001
//
Debug.WriteLine($"Username : {0}", user.Username);
Debug.WriteLine($"Role : {0}", user.Role);
// Setting the new values to the context.
context.Entry(user).State = EntityState.Modified;
This method will work well if you can correctly map your two documents with the camelCase contract resolver.
Enjoy...
Update
I updated the Patch<T>() method with the following code...
public static T PatchObject<T>(T source, JObject document) where T : class
{
Type type = typeof(T);
IDictionary<String, Object> dict =
type
.GetProperties()
.ToDictionary(e => e.Name, e => e.GetValue(source));
string json = document.ToString();
var patchedObject = JsonConvert.DeserializeObject<T>(json);
foreach (KeyValuePair<String, Object> pair in dict)
{
foreach (KeyValuePair<String, JToken> node in document)
{
string propertyName = char.ToUpper(node.Key[0]) +
node.Key.Substring(1);
if (propertyName == pair.Key)
{
PropertyInfo property = type.GetProperty(propertyName);
property.SetValue(source, property.GetValue(patchedObject));
break;
}
}
}
return source;
}

I know I'm a little bit late on this answer, but I think I have a solution that doesn't require having to change serialization and also doesn't include reflection (This article refers you to a JsonPatch library that someone wrote that uses reflection).
Basically create a generic class representing a property that could be patched
public class PatchProperty<T> where T : class
{
public bool Include { get; set; }
public T Value { get; set; }
}
And then create models representing the objects that you want to patch where each of the properties is a PatchProperty
public class CustomerPatchModel
{
public PatchProperty<string> FirstName { get; set; }
public PatchProperty<string> LastName { get; set; }
public PatchProperty<int> IntProperty { get; set; }
}
Then your WebApi method would look like
public void PatchCustomer(CustomerPatchModel customerPatchModel)
{
if (customerPatchModel.FirstName?.Include == true)
{
// update first name
string firstName = customerPatchModel.FirstName.Value;
}
if (customerPatchModel.LastName?.Include == true)
{
// update last name
string lastName = customerPatchModel.LastName.Value;
}
if (customerPatchModel.IntProperty?.Include == true)
{
// update int property
int intProperty = customerPatchModel.IntProperty.Value;
}
}
And you could send a request with some Json that looks like
{
"LastName": { "Include": true, "Value": null },
"OtherProperty": { "Include": true, "Value": 7 }
}
Then we would know to ignore FirstName but still set the other properties to null and 7 respectively.
Note that I haven't tested this and I'm not 100% sure it would work. It would basically rely on .NET's ability to serialize the generic PatchProperty. But since the properties on the model specify the type of the generic T, I would think it would be able to. Also since we have "where T : class" on the PatchProperty declaration, the Value should be nullable. I'd be interested to know if this actually works though. Worst case you could implement a StringPatchProperty, IntPatchProperty, etc. for all your property types.

JSON.Net preserve reference to static object

I am using a variation of the type object pattern (basically smart enums). Since this problem can best be explained with code I will jump right into it.
class Program
{
static void Main(string[] args)
{
Test C = Test.B;
Console.WriteLine(C == Test.B); //Returns true
string Json = JsonConvert.SerializeObject(C);
C = JsonConvert.DeserializeObject<Test>(Json);
Console.WriteLine(C == Test.B); //Returns false
}
}
public class Test
{
public int A { get; set; }
public Test(int A)
{
this.A = A;
}
public static Test B = new Test(100);
}
In this example Test is the type object, and instances of it are assigned to it's static field, B. In real life scenarios there would be multiple of these static fields, each representing a different type. When I serialize and deserialize, the test object is serialized purely as data. I understand why this is happening, but I don't know what to do about it. I would like to somehow preserve instances of Test being references to a static member in that class.

What you are looking for is support for the IObjectReference interface:
Implement this interface on objects that are references to a different object, which cannot be resolved until the current object is completely restored. During the fixup stage, any object implementing IObjectReference is queried for its real object and that object is inserted into the graph.
Unfortunately, Json.NET does not support this interface. However, it turns out to be quite easy to extend Json.NET to support this interface in cases where the type in question also implements ISerializable. This is a quite reasonable restriction given that, in practice, these two interfaces are often used together, as is shown in the documentation example.
First, introduce the following custom contract resolver:
public class ISerializableRealObjectContractResolver : DefaultContractResolver
{
// As of 7.0.1, Json.NET suggests using a static instance for "stateless" contract resolvers, for performance reasons.
// http://www.newtonsoft.com/json/help/html/ContractResolver.htm
// http://www.newtonsoft.com/json/help/html/M_Newtonsoft_Json_Serialization_DefaultContractResolver__ctor_1.htm
// "Use the parameterless constructor and cache instances of the contract resolver within your application for optimal performance."
static ISerializableRealObjectContractResolver instance;
static ISerializableRealObjectContractResolver() { instance = new ISerializableRealObjectContractResolver(); }
public static ISerializableRealObjectContractResolver Instance { get { return instance; } }
public ISerializableRealObjectContractResolver()
: base()
{
this.IgnoreSerializableInterface = false;
}
protected override JsonISerializableContract CreateISerializableContract(Type objectType)
{
var contract = base.CreateISerializableContract(objectType);
var constructor = contract.ISerializableCreator;
contract.ISerializableCreator = args =>
{
var obj = constructor(args);
if (obj is IObjectReference)
{
var context = (StreamingContext)args[1];
obj = ((IObjectReference)obj).GetRealObject(context);
}
return obj;
};
return contract;
}
}
Now, modify your psuedo-enum Test type to implement ISerializable and IObjectReference:
public class Test : ISerializable, IObjectReference
{
readonly int a;
public int A { get { return a; } }
public Test(int A)
{
this.a = A;
}
public static readonly Test B = new Test(100);
#region ISerializable Members
protected Test(SerializationInfo info, StreamingContext context)
{
a = info.GetInt32("A");
}
public void GetObjectData(SerializationInfo info, StreamingContext context)
{
info.AddValue("A", A);
}
#endregion
#region IObjectReference Members
public object GetRealObject(StreamingContext context)
{
// Check all static properties to see whether the key value "A" matches. If so, return the static instance.
if (this.A == B.A)
return B;
return this;
}
#endregion
}
I also made the type immutable since that is clearly the requirement here.
Now your unit test will pass when using this contract resolver:
Test C = Test.B;
Console.WriteLine(C == Test.B); //Returns true
string Json = JsonConvert.SerializeObject(C, new JsonSerializerSettings { ContractResolver = ISerializableRealObjectContractResolver.Instance });
Console.WriteLine(Json);
C = JsonConvert.DeserializeObject<Test>(Json, new JsonSerializerSettings { ContractResolver = ISerializableRealObjectContractResolver.Instance });
Console.WriteLine(C == Test.B); //Still returns true
if (!object.ReferenceEquals(C, Test.B))
{
throw new InvalidOperationException("!object.ReferenceEquals(C, Test.B)");
}
else
{
Console.WriteLine("Global singleton instance deserialized successfully.");
}
Note however that Json.NET only supports the ISerializable interface in full trust.

Not possible by default, since the JSON deserializer doesn't care about existing references or static objects in your class.
You could compare for equality using a custom Equals method, but I guess that isn't what you want.

Don't serialize MyObj.Test, suppress that with an Ignore attribute. Instead, expose a property MyObj.TestID that returns MyObj.Test.ID. When TestID is set on MyObj, load the Test from a static collection keyed by the ID and set MyObj.Test to that value.

First of all, Type Object patterns are supposed to be used when you don't want to go through the inheritance hierarchy every time you define a new derivative of a base class. Having a type object attached as static didn't make sens to be at the first place to be honest. As you mentioned it's a variation Im not going to jump on that.
Looks like you want to be able to keep the reference even after deserialization using json.net.
Now if you want to do that you might want to have a look here.
Taking snippets from the aforementioned link as it's better to have a sample here as this is a StackOverflow answer. It should sustain even the provided link is dead.
Your first option is to use default PreserveReferencesHandling. The associated sample is following where you can reference same objects in a list and point to it. I don't think it actually keeps the old reference but sure helps when you have same things in a list and you dont want to go with your own IEqualityComparer or IEquatable implementations:
string json = JsonConvert.SerializeObject(people, Formatting.Indented,
new JsonSerializerSettings { PreserveReferencesHandling = PreserveReferencesHandling.Objects });
//[
// {
// "$id": "1",
// "Name": "James",
// "BirthDate": "1983-03-08T00:00Z",
// "LastModified": "2012-03-21T05:40Z"
// },
// {
// "$ref": "1"
// }
//]
List<Person> deserializedPeople = JsonConvert.DeserializeObject<List<Person>>(json,
new JsonSerializerSettings { PreserveReferencesHandling = PreserveReferencesHandling.Objects });
Console.WriteLine(deserializedPeople.Count);
// 2
Person p1 = deserializedPeople[0];
Person p2 = deserializedPeople[1];
Console.WriteLine(p1.Name);
// James
Console.WriteLine(p2.Name);
// James
bool equal = Object.ReferenceEquals(p1, p2);
// true
You can use IsReference attribute to control which properties would be kept as references:
[JsonObject(IsReference = true)]
public class EmployeeReference
{
public string Name { get; set; }
public EmployeeReference Manager { get; set; }
}
Now if you want to keep the exact same reference in the code for yourself (I don't think this is really a good design anyway, you might just need a Equality comparison method and be done with it), you need a custom IReferenceResolver defined here.
Furthermore, if you want to have something like that, look no further than Json.net's source code here.
It's an IdReferenceResolver that you can possibly use to preserve your object reference as Guid and possibly use it your way.
And if you want to know how DefaultReferenceResolver works you can have a look at this stackoverflow thread.

Determining object "type" during json deserialization

While trying to de-serialize a complex JSON object (JIRA issue) into an object containing a dictionary of type string-Field I've hit a bit of a bump.
While I can de-serialize various pre-determined object types (standard), I'm having a bit of a harder time with the custom fields, which could be of various types (they all begin with customfield_ followed by a set of numbers).
The custom fields can be floats, strings, booleans, objects and arrays of objects. The latter of these is causing me issues since I can't seem to determine what the object is before I de-serialize it.
I've searched for a way to perhaps "peek" at the data in the object before de-serializing as one of the fields contains information specific to it's type. This is all so I can determine the type of the object and tell Json.Net what to de-serialize it as.
I've considered parsing the JSON string before serialization to get the information, or maybe just when hitting this particular case, but maybe there is a better way?
Thanks in advance for any advice on this.

You can deserialize to an object with Json.Net. Here's a quick and dirty example:
using System;
using Newtonsoft.Json;
namespace Sandbox
{
class Program
{
private static void Main(string[] args)
{
var nestDto = new Dto
{
customfield_1 = 20,
customfield_2 = "Test2"
};
var dto = new Dto
{
customfield_1 = 10,
customfield_3 = new[] { nestDto },
customfield_2 = "Test"
};
var jsonString = JsonConvert.SerializeObject(dto);
Console.WriteLine(jsonString);
var fromJsonString = JsonConvert.DeserializeObject<Dto>(jsonString);
Console.WriteLine(fromJsonString.customfield_3[0].customfield_2); //Outputs Test2
Console.ReadKey();
}
}
class Dto
{
public int customfield_1 { get; set; }
public string customfield_2 { get; set; }
public Dto[] customfield_3 { get; set; }
}
}

Instead of peaking, you can deserialize as the same type as JSON.net uses for ExtensionData explicitly. For example:
if (reader.TokenType == JsonToken.StartArray)
{
var values = serializer.Deserialize<List<Dictionary<string, JToken>>>(reader);
objectContainer = ClassifyAndReturn(values);
}
private ObjectType ClassifyAndReturn(List<Dictionary<string, JToken>> values)
{
if (values.First().ContainsKey("self"))
{
string self = values.First()["self"].Value<string>();
if (self.Contains("customFieldOption"))
//... Then go into a series of if else cases to determine the object.
The representation of the objects are given as a Dictionary of string to JToken, which can then easily be checked and assigned manually or in some cases automatically deserialized (in the case one of the fields is another object).
Here is what an object constructor could look like:
internal myobject(Dictionary<string, JToken> source)
{
Self = source["self"].Value<string>();
Id = source["id"].Value<string>();
Value = source["value"].Value<string>();
}

Deserialisation with JSON.NET - how to handle one name for two possible types?

So, I have some JSON I'm deserialising. Bear in mind I don't have control of the data I'm getting; I just have to work with it as best I can.
It was going fairly well, until I ran into an issue where in an item ("z" below) can be two different types (see "z":[] and "z":{}) within the same item type (in the data I'm dealing with, things should be considered a Dictionary<string, FooType> after deserialisation...).
{
"things":{
"1":{
"x":123.45,
"y":678.90,
"z":{
"2":true
},
"a":[
1,
2
]
},
"2":{
"x":1414.23,
"y":5656.78,
"z":[
true
],
"a":[
3
]
}
}
}
I'm pretty sure this is an output bug (i.e. the source is producing "z":[true] when it should produce "z":{"0":true}) because this is how "z":[true] is to be interpreted later in the application. However, as I said, I don't have control of the data, and the issue is unlikely to be fixed any time soon.
I've tried having a member variable for each, but the naming conflict (from using [DataContract(Name = "z")]) causes an exception (unsurprisingly).
How can I read both types of "z" into a common FooType? (Or equivalent, such as two subclasses of a common FooParentType that somehow get applied only in the correct cases...)
EDIT: I'd prefer to achieve the desired result as part of the deserialisation process, without preprcossing the string (although if there are no other ways, I'll go there, I guess...)
I'm using C#, Mono, JSON.NET, and using code like so (compilable version on pastebin):
string jsonString = "{\"things\":{\"1\":{\"x\":123.45,\"y\":678.9,\"z\":{\"2\":true},\"a\":[1,2]},\"2\":{\"x\":1414.23,\"y\":5656.78,\"z\":[true],\"a\":[3]}}}";
RootType rt = JsonConvert.DeserializeObject<RootType>(jsonString);
With classes:
[DataContract]
class RootType
{
[DataMember(IsRequired = true)]
public Dictionary<string, FooType> things { get; set; }
}
[DataContract]
class FooType
{
[DataMember(IsRequired = true)]
public double x { get; set; }
[DataMember(IsRequired = true)]
public double y { get; set; }
[DataMember(IsRequired = true)]
public List<int> a { get; set; }
// List<bool> zList and Dictionary<string, bool> zDict each only work for one case
// but not the other, and having both causes a naming conflict
}

I had a similar issue and simply ran the string through a string.replace function to "correct" the data prior to deserializing.