CODEWITHSUNDEEP
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Reputation: 62712

How to define the protobuf-net model with a generic base class?

Given these types:

  [DataContract]
  public class EntityId
  {
    [DataMember(Order = 1)]
    public string IdAsString { get; set; }
    [DataMember(Order = 2), XmlIgnore]
    public Type Type { get; set; }

    #region XML hacks

    [XmlElement("Type"), Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]
    public string AssemblyQualifiedTypeName
    {
      get { return ValueConverter.Default.Type2String(Type); }
      set { Type = ValueConverter.Default.String2Type(value); }
    }

    #endregion
  }

  [DataContract]
  public class EntityRelation
  {
    [DataMember(Order = 1)]
    public int Id { get; set; }
    [DataMember(Order = 2)]
    public string Path { get; set; }
  }

  [DataContract]
  public class Base<TId>
  {
    [DataMember(Order = 1)]
    public TId Id { get; set; }
    [DataMember(Order = 2)]
    public string Name { get; set; }
    [DataMember(Order = 3)]
    public EntityId ParentId { get; set; }
    [DataMember(Order = 4)]
    public int LastChanged { get; set; }
    [DataMember(Order = 5)]
    public string Description { get; set; }
    [DataMember(Order = 6)]
    public EntityRelation EntityRelation { get; set; }
  }

  [DataContract]
  public class FlowFolder : Base<int>
  {
  }

This model definition:

  var m = RuntimeTypeModel.Default;
  m.AutoCompile = false;
  m.Add(typeof(Base<int>), true).AddSubType(1, typeof(FlowFolder));

And this usage:

var entity = GetFlowFolder();
var typeTag = GetTypeTag(entity);
Model.SerializeWithLengthPrefix(stream, entity, null, PrefixStyle.Base128, typeTag);

I get this exception:

System.InvalidOperationException occurred
  Message=Duplicate field-number detected; 1 on: NC.DTO.Base`1[[System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]
  Source=protobuf-net
  StackTrace:
       at ProtoBuf.Serializers.TypeSerializer..ctor(Type forType, Int32[] fieldNumbers, IProtoSerializer[] serializers, MethodInfo[] baseCtorCallbacks, Boolean isRootType, Boolean useConstructor, CallbackSet callbacks, Type constructType) in z:\Work\protobuf-net-v2\protobuf-net\Serializers\TypeSerializer.cs:line 43
  InnerException:

With the following stack trace:

protobuf-net.dll!ProtoBuf.Serializers.TypeSerializer.TypeSerializer(System.Type forType, int[] fieldNumbers, ProtoBuf.Serializers.IProtoSerializer[] serializers, System.Reflection.MethodInfo[] baseCtorCallbacks, bool isRootType, bool useConstructor, ProtoBuf.Meta.CallbackSet callbacks, System.Type constructType) Line 43   C#
protobuf-net.dll!ProtoBuf.Meta.MetaType.BuildSerializer() Line 283 + 0xe3 bytes C#
protobuf-net.dll!ProtoBuf.Meta.MetaType.Serializer.get() Line 209 + 0x11 bytes  C#
protobuf-net.dll!ProtoBuf.Meta.RuntimeTypeModel.Serialize(int key, object value, ProtoBuf.ProtoWriter dest) Line 357 + 0x51 bytes   C#
protobuf-net.dll!ProtoBuf.ProtoWriter.WriteObject(object value, int key, ProtoBuf.ProtoWriter writer, ProtoBuf.PrefixStyle style, int fieldNumber) Line 101 + 0x45 bytes    C#
protobuf-net.dll!ProtoBuf.Meta.TypeModel.SerializeWithLengthPrefix(System.IO.Stream dest, object value, System.Type type, ProtoBuf.PrefixStyle style, int fieldNumber, ProtoBuf.SerializationContext context) Line 467 + 0x24 bytes C#
protobuf-net.dll!ProtoBuf.Meta.TypeModel.SerializeWithLengthPrefix(System.IO.Stream dest, object value, System.Type type, ProtoBuf.PrefixStyle style, int fieldNumber) Line 435 + 0x32 bytes    C#

I am using rev 424.

What am I doing wrong?

Thanks.

EDIT

I do not understand anything. It does not work if I make Base<T> a non generic type as well. I must be missing something really basic here.

EDIT2

Debugging the code reveals that field numbers of the base type properties are collected in the same list with the field numbers of the derived types. From that I deduce that the only way for the inheritance to work is with surrogates. At least in revision 424.

Upvotes: 2

Views: 2714

Answers (1)

Marc Gravell
Marc Gravell

Reputation: 1062492

.AddSubType(1, typeof(FlowFolder)); vs [DataMember(Order = 1)]

The field-number used to identify a sub-type must not conflict with any defined fields on that same type. Just use a number that doesn't conflict. The conflict only applies to that type - it doesn't have to be unique among the sub-types; for example, .AddSubType(8, typeof(FlowFolder)); would be fine, and it would not matter whether FlowFolder had a "field 8".

From that I deduce that the only way for the inheritance to work is with surrogates.

I don't see how that follows....?

Upvotes: 3

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