Issues with deserializing MessagePack objects

[koopmansrw]

Hi,

I'm new to MessagePack and I have a few issues at hand. I'm receiving data but when I'm trying to Deserialize the data to a [MessagePack] object, I get the "MessagePackSerializationException: Unexpected msgpack code 138 (fixmap) encountered.". Even with the simplest of classes I cannot get this to work.

I cannot control what is being sent, as this is done by another party, and I cannot really find any help on how to properly configure it on my end. I'm using .NET 8.0 as it's going to run on a Linux server.

My testclass:

[MessagePackObject] public class MyClass { [Key(1)] public Int64 DeviceId { get; set; } }

Deserializing it to a dynamic or an object does work, however the values I get often contain replacement characters. There is a field which contain bytearrays of data, but converting it to a dynamic or object, results in this field being deserialized as an array of object, causing data loss.

Calling the deserialization as dynamic:

var obj = MessagePackSerializer.Deserialize<dynamic>(bytes);

and the resulting Key 34 which is parsed as an object array causing dataloss.

I'm not sure the data loss is even related to MessagePack, but any help would be greatly appreciated.

[koopmansrw]

I've tried different MessagePack library, which does return proper data for indices 1 and 5:
0xC000BE025802 and 0x9A009A2600003831313030393830313433354456303830372323000008001000810003270A270327AC26. Is there any way I can fix this?

[AArnott]

Unexpected msgpack code 138 (fixmap) encountered

This suggests the msgpack you're trying to deserialize is using a map. But your MyClass definition is using [Key] attributes which means this library is going to expect to see an array.

Try removing the Key attributes, and change [MessagePackObject] to [MessagePackObject(true)].

[koopmansrw]

The I get a resolver error. The decoded messagepack actually looks similar to this (just a few fields, for the general idea). That's why I used the Key("0") etc.

{
"0": 1,
"1": 868446031294156,
"4": 1756966840,
}

[AArnott]

Per your original post, you used [Key(1)] which is not the same as [Key("1")] which in your reply you claimed you used.

The map you shared just now suggests strings are used (although, it's hard to know for sure, because you're showing it as JSON and JSON doesn't allow non-string keys), in which case you need to specify [Key("1")] (a string key).

[koopmansrw]

Ah, yeah I got this from the MessagePack Lite site. But mapping the data as a Dictionary has the keys as integers. Tried both, both not working, probably because the sending party does things slightly different. Thanks anyway!