Automapper exception when mapping JsonObject in .Net6 - "The node already has a parent"

Question

I'm trying to map a JsonObject (System.Text.Json) with AutoMapper 12.0.0

Source:

public record Request
    {
        public Guid RequestId { get; set; }
        public JsonObject AdditionalParameters { get; set; }
    }

Destination:

public record ResultsEvent
{
    public Guid RequestId { get; init; }
    public JsonObject AdditionalParameters { get; init; }
}

The code which getting an error is the following:

var resultsEvent = _mapper.Map<ResultsEvent>(request);

The error I get:

---> System.InvalidOperationException: The node already has a parent.
at System.Text.Json.ThrowHelper.ThrowInvalidOperationException_NodeAlreadyHasParent()
at System.Text.Json.Nodes.JsonNode.AssignParent(JsonNode parent)
at lambda_method319(Closure , Object , ResultsEvent, ResolutionContext )
--- End of inner exception stack trace ---

I saw the following answer but I wonder if there is a more elegant way than setting it manually.

Just for clarity, with NewtonSoft.Json I don't get this error.

I tried to clone it in the AutoMapper profile and serializing/deserializing but nothing worked.

Yes show something that is reproducable. So add the profile with the actual mapping and some example data. — Ralf
– Ralf, Commented Mar 29, 2023 at 13:05
Hard o say without a minimal reproducible example showing sample JSON and how _mapper is constructed, but the The node already has a parent. exception is thrown when trying to add a JsonNode that already has a parent, to another parent. You may need to teach AutoMapper how to map JsonNode objects yourself. See Clone a JsonNode and attach it to another one in .NET 6. — dbc
– dbc, Commented Mar 29, 2023 at 15:13

Aleksandr Tereshchenko · Accepted Answer · 2023-03-29 15:38:14Z

1

The more elegant way is just configure additional map for the JsonObject

expression.CreateMap<JsonObject, JsonObject>()
          .ConvertUsing(src => JsonNode.Parse(src.ToJsonString(JsonSerializerOptions.Default), 
                                              null, default)
          .AsObject());

answered Mar 29, 2023 at 15:38

Aleksandr Tereshchenko

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