MessagePackDynamicObjectResolverException: can't find matched constructor. type:System.Text.Json.JsonElement about messagepack-csharp

[AArnott]

At least the following works perfectly fine if I rename @namespace and the corresponding property to something different:

Ok, my curiosity is peaked. If you send me a minimal repro I'll be happy to take a look.

[AArnott]

The @ prefix isn't part of the parameter name. That's just C# syntax. At runtime, where MessagePack is reflecting over your members, there is no @ character. So that's not the problem.

Why are you using the JsonConstructor attribute if you're using MessagePack? In fact I don't see any messagepack attributes at all on this class, so I wonder why you expect it to work.
You mention using Typeless. But to work without attributes, you need to write a custom formatter, or use the Contractless resolver.

[flobernd]

@AArnott Thanks for the reply.

The @ prefix isn't part of the parameter name. That's just C# syntax. At runtime, where MessagePack is reflecting over your members, there is no @ character. So that's not the problem.

I admit, I have not checked in detail and I know the verbatim operator is just an escape character, but I was thinking it might probably get included in the name that is reported by reflection or something similar.

Why are you using the JsonConstructor attribute if you're using MessagePack?

The whole reason for me to use MessagePack is for caching reasons. I load a huge JSON payload with System.Text.Json. This process is quite slow compared to the binary deserialization MessagePack offers.

In fact I don't see any messagepack attributes at all on this class, so I wonder why you expect it to work.
You mention using Typeless. But to work without attributes, you need to write a custom formatter, or use the Contractless resolver.

I don't think this is true. At least the following works perfectly fine if I rename @namespace and the corresponding property to something different:

var data = await MessagePackSerializer.Typeless
    .DeserializeAsync(fs, default, cancellationToken)
    .ConfigureAwait(false);

I'm not using any attributes (for now) because the JSON payload is pretty complex and consists of 50-100 sub-classes which I didn't want to annotate during the evaluation/test phase for MessagePack 🙂