JSON.Net: deserializing polymorphic types without specifying the assembly
- by Frank Schwieterman
I see that using JSON.Net, I can decode polymorphic objects if a $type attribute specifies the specific type of the JSON object. In all the examples I've seen, $type includes the namespace. Is it possible to make this work including just a simple typename without the assembly? I'd be happy to specify a default assembly to the JsonSerializer if thats possible
I am able to deserialize the JSON using:
public class SingleAssemblyJsonTypeBinder : SerializationBinder
{
private readonly Assembly _assembly;
private Dictionary _typesBySimpleName = new Dictionary(StringComparer.OrdinalIgnoreCase);
private Dictionary _simpleNameByType = new Dictionary();
public SingleAssemblyJsonTypeBinder(Assembly assembly)
{
_assembly = assembly;
_typesBySimpleName = new Dictionary<string, Type>();
foreach (var type in _assembly.GetTypes().Where(t => t.IsPublic))
{
if (_typesBySimpleName.ContainsKey(type.Name))
throw new InvalidOperationException("Cannot user PolymorphicBinder on a namespace where multiple public types have same name.");
_typesBySimpleName[type.Name] = type;
_simpleNameByType[type] = type.Name;
}
}
public override Type BindToType(string assemblyName, string typeName)
{
Type result;
if (_typesBySimpleName.TryGetValue(typeName.Trim(), out result))
return result;
return null;
}
public override void BindToName(Type serializedType, out string assemblyName, out string typeName)
{
string name;
if (_simpleNameByType.TryGetValue(serializedType, out name))
{
typeName = name;
assemblyName = null;// _assembly.FullName;
}
else
{
typeName = null;
assemblyName = null;
}
}
}
...
public static JsonSerializerSettings GetJsonSerializationSettings()
{
var settings = new JsonSerializerSettings();
settings.Binder = new SingleAssemblyJsonTypeBinder(typeof(MvcApplication).Assembly);
settings.TypeNameHandling = TypeNameHandling.Objects;
return settings;
}
....
var serializer = JsonSerializer.Create(settings);
I haven't been able to make this work with MVC though, I'm configuring json deserialization per the code below in Application_Start, and the object is deserialized, but using the base type one.
GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.Binder = new SingleAssemblyJsonTypeBinder(this.GetType().Assembly);
GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.TypeNameHandling = TypeNameHandling.All;
GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.TypeNameAssemblyFormat = FormatterAssemblyStyle.Simple;
