Protobuf-net serialization without annotation

Question

I looked at this answer and I am in a situation where I don't need to maintain backward compatibility and I have to have a solution that works without having to decorate dozens of classes with the attributes needed for protobuf-net. So I tried using RuntimeTypeModel.Default.InferTagFromNameDefault = true; but I may be not using it correctly because the Serializer.Serialize call still throws an exception asking for a contract. Here is my quick test, what am I doing wrong?

public enum CompanyTypes
{
    None, Small, Big, Enterprise, Startup
}

public class BaseUser
{
    public string SSN { get; set; }    
}

public class User : BaseUser
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public int Age { get; set; }
    public DateTime BirthDate { get; set; }
    public List<string> Friends { get; set; }
    public Company Company { get; set; }
}

public class Company
{
    public string Name { get; set; }
    public string Address { get; set; }
    public CompanyTypes Type { get; set; }
    public List<Product> Products { get; set; }
}

public class Product
{
    public string Name { get; set; }
    public string Sku { get; set; }
}

[TestClass]
public class SerializationTest
{
    [TestMethod]
    public void SerializeDeserializeTest()
    {
        var user = new User
                       {
                           Age = 10,
                           BirthDate = DateTime.Now.AddYears(-10),
                           FirstName = "Test First",
                           LastName = "Test Last",
                           Friends = new List<string> { "Bob", "John" },
                           Company = new Company
                                         {
                                             Name = "Test Company",
                                             Address = "Timbuktu",
                                             Type = CompanyTypes.Startup,
                                             Products = new List<Product>
                                             {
                                                new Product{Name="Nerf Rocket", Sku="12324AC"},
                                                new Product{Name="Nerf Dart", Sku="DHSN123"}
                                             }
                                         }
                       };

        RuntimeTypeModel.Default.InferTagFromNameDefault = true;
        using (var memoryStream = new MemoryStream())
        {
            Serializer.Serialize(memoryStream, user);
            var serialized = Convert.ToBase64String(memoryStream.GetBuffer(), 0, (int)memoryStream.Length);
        }
    }
}

Answer 1

InferTagFromName (and it's twin, InferTagFromNameDefault) only take a hand when it is necessary to resolve a tag number for a member; they don't influence which members need to be serialized (so currently the answer to that would be: none, even if the system knew about them). The option you might have chosen would be ImplicitFields, but that is currently only available as a [ProtoContract(...)] marker. If you don't mind a little annotation, a pragmatic fix may be:

[ProtoContract(ImplicitFields = ImplicitFields.AllPublic)]

on User, Company and Product, and something a bit more complex for BaseUser (because of the inheritance):

[ProtoContract(ImplicitFields = ImplicitFields.AllPublic, ImplicitFirstTag = 10)]
[ProtoInclude(1, typeof(User))]

Note we haven't had to add lots of per-member annotation. If you are really really anti-attributes, then it is also possible to configure the entire model through code, via:

RuntimeTypeModel.Default.Add(typeof(Product), false).Add("Name", "Sku");
RuntimeTypeModel.Default.Add(typeof(Company), false).Add("Name", "Address",
         "Type", "Products");
RuntimeTypeModel.Default.Add(typeof(User), false).Add("FirstName", "LastName",
         "Age", "BirthDate", "Friends", "Company");
RuntimeTypeModel.Default.Add(typeof(BaseUser), false).Add(10, "SSN")
         .AddSubType(1, typeof(User));

Answer 2

The question is old, but maybe someone will need this. I implemented ProtobufSerializer class which will construct your Type graph upon use. You just need to annotate your DTO with [KnownTypeAttribute] and [DataMember]/[IgnoreDataMember] attributes. Mostly this is refactored version of another nuget project from some guy. This way you don't need to include protobuf in your contract dependencies:

    internal sealed class ProtobufSerializer
    {
        private readonly RuntimeTypeModel _model;
        private const BindingFlags Flags = BindingFlags.FlattenHierarchy | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance;
        private readonly Dictionary<Type, HashSet<Type>> _subTypes = new Dictionary<Type, HashSet<Type>>();
        private readonly ConcurrentDictionary<Type, bool> _builtTypes = new ConcurrentDictionary<Type, bool>();
        private static readonly Type[] ComplexPrimitives = new [] { typeof(object), typeof(ValueType), typeof(Enum), typeof(Array)};
        private readonly object _sync = new object();

        public ProtobufSerializer()
        {
            _model = TypeModel.Create();
        }

        public void Serialize(Stream s, object input)
        {
            EnsureType(input.GetType());
            _model.Serialize(s, input);
        }

        public T Deserialize<T>(Stream s)
        {
            EnsureType(typeof(T));
            return (T)_model.Deserialize(s, null, typeof(T));
        }

        public void EnsureType(Type type)
        {
            if (_builtTypes.ContainsKey(type))
            {
                return;
            }
            lock (_sync)
            {
                if (_builtTypes.ContainsKey(type))
                {
                    return;
                }
                var all = GetGraph(type).ToArray();
                foreach (var t in all)
                {
                    InternalBuild(t);
                }
            }
        }

        private void InternalBuild(Type type)
        {
            if (IsPrimitive(type))
            {
                return;
            }

            FlatBuild(type);
            EnsureBaseClasses(type);
            EnsureGenerics(type);

            _builtTypes.TryAdd(type, false);
        }

        private bool IsPrimitive(Type type)
        {
            return type == null || type.IsPrimitive || _model.CanSerializeBasicType(type) || _builtTypes.ContainsKey(type) || ComplexPrimitives.Contains(type);
        }

        private static IEnumerable<Type> GetGraph(Type type)
        {
            return type.TraverseDistinct(GetConnections).Distinct().OrderBy(x=> x.FullName);
        }

        private static Type GetParent(Type type)
        {
            return type.BaseType;
        }

        private static IEnumerable<Type> GetChildren(Type type)
        {
            var knownTypes = type.GetCustomAttributes(typeof(KnownTypeAttribute)).Cast<KnownTypeAttribute>().Select(x => x.Type).ToArray();
            foreach (var t in knownTypes)
            {
                yield return t;
            }

            var fields = GetFields(type);
            var props = GetProperties(type);
            foreach (var memberType in fields.Select(f => f.FieldType))
            {
                yield return memberType;
            }
            foreach (var memberType in props.Select(f => f.PropertyType))
            {
                yield return memberType;
            }
        }

        private static IEnumerable<Type> GetConnections(Type type)
        {
            var parent = GetParent(type);
            if (parent != null)
            {
                yield return parent;
            }
            var children = GetChildren(type);
            if (children != null)
            {
                foreach (var c in children)
                {
                    yield return c;
                }
            }
        }

        private void FlatBuild(Type type)
        {
            if(type.IsAbstract)
                return;

            var meta = _model.Add(type, false);
            var fields = GetFields(type);
            var props = GetProperties(type);
            meta.Add(fields.Select(m => m.Name).ToArray());
            meta.Add(props.Select(m => m.Name).ToArray());
            meta.UseConstructor = false;
            foreach (var memberType in fields.Select(f => f.FieldType).Where(t => !t.IsPrimitive))
            {
                InternalBuild(memberType);
            }
            foreach (var memberType in props.Select(f => f.PropertyType).Where(t => !t.IsPrimitive))
            {
                InternalBuild(memberType);
            }
        }

        private static FieldInfo[] GetFields(Type type)
        {
            return type.GetFields(Flags).Where(x => x.IsDefined(typeof(DataMemberAttribute))).Where(x => !x.IsDefined(typeof(IgnoreDataMemberAttribute))).ToArray();
        }

        private static PropertyInfo[] GetProperties(Type type)
        {
            return type.GetProperties(Flags).Where(x => x.IsDefined(typeof(DataMemberAttribute))).Where(x=> !x.IsDefined(typeof(IgnoreDataMemberAttribute))).ToArray();
        }

        private void EnsureBaseClasses(Type type)
        {
            var baseType = type.BaseType;
            var inheritingType = type;


            while (!IsPrimitive(baseType))
            {
                HashSet<Type> baseTypeEntry;

                if (!_subTypes.TryGetValue(baseType, out baseTypeEntry))
                {
                    baseTypeEntry = new HashSet<Type>();
                    _subTypes.Add(baseType, baseTypeEntry);
                }

                if (!baseTypeEntry.Contains(inheritingType))
                {
                    InternalBuild(baseType);
                    _model[baseType].AddSubType(baseTypeEntry.Count + 500, inheritingType);
                    baseTypeEntry.Add(inheritingType);
                }

                inheritingType = baseType;
                baseType = baseType.BaseType;
            }
        }

        private void EnsureGenerics(Type type)
        {
            if (type.IsGenericType || (type.BaseType != null && type.BaseType.IsGenericType))
            {
                var generics = type.IsGenericType ? type.GetGenericArguments() : type.BaseType.GetGenericArguments();

                foreach (var generic in generics)
                {
                    InternalBuild(generic);
                }
            }
        }
    }

And also some simple extensions:

    public static IEnumerable<T> TraverseDistinct<T>(this T enumer, Func<T, IEnumerable<T>> getChildren)
    {
        return new[] { enumer }.TraverseDistinct(getChildren);
    }
    public static IEnumerable<T> TraverseDistinct<T>(this IEnumerable<T> enumer, Func<T, IEnumerable<T>> getChildren)
    {
        HashSet<T> visited = new HashSet<T>();
        Stack<T> stack = new Stack<T>();
        foreach (var e in enumer)
        {
            stack.Push(e);
        }
        while (stack.Count > 0)
        {
            var i = stack.Pop();
            yield return i;
            visited.Add(i);

            var children = getChildren(i);
            if (children != null)
            {
                foreach (var child in children)
                {
                    if (!visited.Contains(child))
                    {
                        stack.Push(child);
                    }
                }
            }
        }
    }

Answer 3

It's quite experimental at this phase but I've made a small library that takes most Types and generates the Protobuf-net serializers at run-time: https://github.com/fnicollier/AutoProtobuf