ServiceStack Dto can't have object[] but int[] is Ok?

Question

Works:

[ProtoContract(ImplicitFields = ImplicitFields.AllPublic)]
public class ExcelData
{
    public int[] DataObjects { get; set; }
}

Don't work:

[ProtoContract(ImplicitFields = ImplicitFields.AllPublic)]
public class ExcelData
{
    public object[] DataObjects { get; set; }
}

My test:

[TestMethod]
public void ProtoWithObjectArray()
{
   var ex = new ProtoBufServiceClient(baseUrl);
   var res = ex.Get(new SelectWorksheetRange());
}

[ProtoContract(ImplicitFields = ImplicitFields.AllPublic)]
public class SelectWorksheetRange : IReturn<ExcelData>
{
}

I don't even see error, because test just finish at ex.Get without any information. How to debug this?

There are no assertions in the test method. Are you just breakpointing at "var res = ..."? — Hans, Mar 16 '14 at 01:45
@Hans Yes, it seems that I can't transfer object via protobuf. — Tomasito, Mar 16 '14 at 11:56
If you can ever avoid using plain old "object", then you should (locks being the exception). — Hans, Mar 18 '14 at 02:05
@Hans after reading from Excel service I'm creating my own DTO (without object) and using them. — Tomasito, Mar 18 '14 at 11:11

score 1 · Accepted Answer · answered Mar 16 '14 at 09:26

1

I cannot comment on ServiceStack, but as far as protobuf-net is concerned, yes: "int[] good, object[] bad". The reason is that the protobuf wire format (as designed by Google) is very terse and includes precisely zero metadata: it expects both ends of any conversation to know exactly what they are exchanging at any point. With int[], that is possible, and with object[] it simply isn't. There are some nasty ways of hacking around it, but they tend to be problematic (maintenance-wise) and inefficient.

answered Mar 16 '14 at 09:26

Marc Gravell

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Solution is to cast `object[]` as `byte[]` and transfer bytes? It is very simple thought. – Tomasito Mar 16 '14 at 12:04
@Tomasito that would only work if the data always actually is of the cast type. And if it is: it should be declared as such in the first place. Finally, correct me if I am wrong, but IIRC array variance only applies to arrays of reference types. Byte is not a reference type. – Marc Gravell Mar 16 '14 at 13:02
I'm writing service to share Excel worksheet data. This service is then used by another services and they will do casting from `object[]` to something meaningful. And all Excel interop functions returns objects. Now is OK when I put object[] into `MemoryStream` – Tomasito Mar 16 '14 at 13:26
@Tomasito at no point does one "put object[] into MemoryStream". A memory stream wraps a byte buffer: nothing more. Sure you can *serialize* to a memory-stream, but then you need to follow the rules of the chosen serilaizer. For this reason, it is not uncommon to use different DTO models with different serializers in a single application. – Marc Gravell Mar 16 '14 at 19:11

ServiceStack Dto can't have object[] but int[] is Ok?

1 Answers1