Json Deserialization of "dynamic" does not work

[MhAllan]

Description

With Newtonsoft:

var obj = JsonConvert.DeserializeObject<dynamic>("{ x: "something" }");

You will get correct dynamic object with obj.x being something.

but using Text.Json serializer you get obj.x to be null or empty array []

Reproduction Steps

deserialize string to dynamic

Expected behavior

to get dynamic object with dynamic properties have correct values

Actual behavior

we get dynamic object but with empty properties or properties assigned to empty arrays

Regression?

No response

Known Workarounds

use Newtonsoft

Configuration

No response

Other information

No response

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Issue Details

---

Description

With Newtonsoft:

var obj = JsonConvert.DeserializeObject<dynamic>("{ x: "something" }");

You will get correct dynamic object with obj.x being something.

but using Text.Json serializer you get obj.x to be null or empty array []

Reproduction Steps

deserialize string to dynamic

Expected behavior

to get dynamic object with dynamic properties have correct values

Actual behavior

we get dynamic object but with empty properties or properties assigned to empty arrays

Regression?

No response

Known Workarounds

use Newtonsoft

Configuration

No response

Other information

No response

Author:	MhAllan
Assignees:	-
Labels:	area-System.Text.Json, untriaged
Milestone:	-

[huoyaoyuan]

There's no dynamic support currently in System.Text.Json. See #66517 #53195.
For dynamic behavior, you can serialize it as JsonElement or JsonNode, and use indexer to access its properties. No support for C# dynamic syntax now.

[eiriktsarpalis]

Closing as by-design behavior.

[MhAllan]

@huoyaoyuan, @eiriktsarpalis so basically things like CosmosDB and the way we design unstructured data in it will stay with Newtonsoft forever?

[huoyaoyuan]

You can use indexer syntax (node["a"]), though very verbose.
I'm not the designer, but I will vote for supporting dynamic.

[MhAllan]

@huoyaoyuan yeah I don't see a reason why not if Newtonsoft got it right. There are lot of serialization that require dynamic objects especially when you deal with nosql and different types of message queues. no dynamic serialization means all these technical and business pieces can't use Text.Json

[eiriktsarpalis]

I've unlocked the discussion in #53195, feel free to contribute to the discussion there if there's anything more to add.