Inheritance and the JSON formatter of ASP.NET Web API

Question

Imagine a simple controller action IEnumerable<BaseType> Get(). It returns an enumeration of different types all deriving from BaseType.

When the client requests XML, the result is something like this:

<ArrayOfBaseType>
    <BaseType i:type="DerivedType1"><A>value</A></BaseType>
    <BaseType i:type="DerivedType2"><B>value</B></BaseType>
    <BaseType i:type="DerivedType3"><C>value</C></BaseType>
</ArrayOfBaseType>

As you can see, the type of the derived class is transmitted in the i:type attribute.

If the client requests JSON however, this information is missing:

[
  {"A":"value"},
  {"B":"value"},
  {"C":"value"}
]

How to fix this?

@downvoter: Without an explanation, your downvote is worth nothing as I can't improve the question without knowing what is unclear. — Daniel Hilgarth
– Daniel Hilgarth, Commented Sep 29, 2012 at 11:50

Daniel Hilgarth · Accepted Answer · 2012-10-09 10:45:40Z

4

The following change is necessary:

In the WebApiConfig.cs the following line needs to be added:

config.Formatters.JsonFormatter.SerializerSettings.TypeNameHandling = 
    TypeNameHandling.Auto;

This will automatically result in a new property $type when needed.

answered Oct 9, 2012 at 10:45

Daniel Hilgarth

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Comments

Khurshid · Accepted Answer · 2012-09-29 11:21:07Z

0

If you write your class following:

public class MyClass
{
    // properties here

    public string IType
    {
        get
        {
            return this.GetType().Name;
        }

        set {  }
    }
}

Maybe, it will help you

edited Sep 29, 2012 at 11:21

answered Sep 29, 2012 at 10:36

Khurshid

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2 Comments

Daniel Hilgarth Over a year ago

Not really. In my eyes that's a hack.

Khurshid Over a year ago

I'm not sure with json exists another way.

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