devoyster

var model = RuntimeTypeModel.Default;

// Obtain all serializable types having no explicit proto contract
var serializableTypes = Assembly.GetExecutingAssembly()
    .GetTypes()
    .Where(t => t.IsSerializable && !Attribute.IsDefined(t, typeof(ProtoContractAttribute)));
foreach (var type in serializableTypes)
{
    var metaType = model.Add(type, false);
    metaType.AsReferenceDefault = true;