.net 6 broken migration JsonElement to dynamic

[devopg]

I come from .net core 2.1 and after migration to .net 6 i got different behavior.

I have json in my RabbitMQ. After cunsume new message i deserialize to class with field List

class msg{
   public string Name {get;set;}
   public int Old {get;set;}
   ... other fiedls 
   public List<dynamic> list {get;set;}
}

Working code from 2.1 now throw error

    foreach (var i in msg.list)
    {
        switch ((VariantEnum)i.variant)

In debug i found that now "var i" is typeof JsonElement

How i can in .net 6 use dynamic like before ?

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Issue Details

---

I come from .net core 2.1 and after migration to .net 6 i got different behavior.

I have json in my RabbitMQ. After cunsume new message i deserialize to class with field List

class msg{
   public string Name {get;set;}
   public int Old {get;set;}
   ... other fiedls 
   public List<dynamic> list {get;set;}
}

Working code from 2.1 now throw error

    foreach (var i in msg.list)
    {
        switch ((VariantEnum)i.variant)

In debug i found that now "var i" is typeof JsonElement

How i can in .net 6 use dynamic like before ?

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

[jkoritzinsky]

Related issue: #53195

[devopg]

Related issue: #53195

i didnt find there (#53195) how fix my problem only bla bla bla

[huoyaoyuan]

Which serializer are you using? The serialization to an object supports dynamic is done by the serializer.

[eiriktsarpalis]

In debug i found that now "var i" is typeof JsonElement

Echoing @huoyaoyuan's comment, what serializer is you .NET Core 2.1 application using? STJ has always used JsonElement by default when handling unknown types. Could you share a minimal reproduction demonstrating the behavior in .NET Core 2.1?

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[devopg]

In debug i found that now "var i" is typeof JsonElement

Echoing @huoyaoyuan's comment, what serializer is you .NET Core 2.1 application using? STJ has always used JsonElement by default when handling unknown types. Could you share a minimal reproduction demonstrating the behavior in .NET Core 2.1?

In 2.1 i use
using Newtonsoft.Json;

JsonConvert.SerializeObject(obj, Formatting.Indented,
                new JsonSerializerSettings {
                    ReferenceLoopHandling = ReferenceLoopHandling.Ignore
                });

return JsonConvert.DeserializeObject<T>(str);

[eiriktsarpalis]

Feature parity with Json.NET is not a design goal for System.Text.Json. Per #53195 an explicit design decision was made to not support dynamic. It is still possible to deserialize into dynamic however as you point out values as represented using JsonElement.