JSON.NET - exclude properties of a specific type at runtime

Question

I'm wondering how to exclude/strip certain properties of given type(s) (or collections of those) from being serialized using Json.NET library? I tried to write my own contract resolver (inheriting from DefaultContractResolver) with no luck.

I know that I could be done using DataAnnotations, decorating the excluded properties with ScriptIgnoreAttribute, but it's not applicable in my scenario. The objects serialized can be virtually anything, so I don't know which properties to exclude at design-time. I know only the types of properties that should not be serialized.

It looks like a rather simple task, but unfortunately I couldn't find a decent solution anywhere...

BTW - I'm not bound to Json.NET library - if it can easily be done with default/other .NET JSON serializers it'd be an equally good solution for me.

UPDATE

The properties has to be excluded before trying to serialize them. Why?

Basically, the types of objects I'm receiving and serializing can have dynamic properties of type inheriting from IDynamicMetaObjectProvider. I'm not going to describe all the details, but the DynamicMetaObject returned from GetMetaObject method of these objects doesn't have DynamicMetaObject.GetDynamicMemberNames method implemented (throws NotImplementedException...). Summarizing - the problem is those objects (I need to exclude) doesn't allow to enumerate their properties, what Json.NET serializer tries to do behind the scenes. I always end up with NotImplementedException being thrown.

Answer 1

I have tried both the WCF JSON serialization as well as the System.Web.Script.Serialization.JavaScriptSerializer. I have found if you want solid control of the serialization process and do not want to be bound by attributes and hacks to make things work, the JavaScriptSerializer is the way to go. It is included in the .NET stack and allows you to create and register JavaScriptConverter subclasses to perform custom serialization of types.

The only restriction I have found that may cause you a problem is that you cannot easily register a converter to convert all subclasses of Object (aka, one converter to rule them all). You really need to have knowledge of common base classes or preregister the set of types up front by scanning an assembly. However, property serialization is entirely left up to you, so you can decide using simple reflection which properties to serialize and how.

Plus, the default serialization is much much much better for JSON than the WCF approach. By default, all types are serializable without attributes, enums serialize by name, string-key dictionaries serialize as JSON objects, lists serialize as arrays, etc. But for obvious reasons, such as circular trees, even the default behavior needs assistance from time to time.

In my case, I was supporting a client-API that did not exactly match the server class structure, and we wanted a much simpler JSON syntax that was easy on the eyes, and the JavaScriptSerializer did the trick every time. Just let me know if you need some code samples to get started.

Answer 2

Create your own contract resolver, override the method that creates the properties for an object and then filter the results to only include those that you want.