System.Text.Json.Serialization not Deserialize inheritance class

[psychomonkey9]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

i have class:

public class SomeClass
    {
        public int Id { get; set; }
    
        public string Name { get; set; }
    
        [JsonConverter(typeof(ParameterConverter))]
        public Parameter parameter1{ get; set; }
    }
    
    public class Parameter
    {
       public ParameterType FieldType { get; set; }
    };
        
    public class FieldParameter : Parameter
    {
       public string FieldId { get; set; }
    }
    
    public enum ParameterType
    {
        Default,
        Field
    }

and this is example json:

{
      "id": 1,
      "name": "SomeName"
      "parameter1": {
        "fieldId": "SomeId",
  	  "fieldType": "Field"
      }
  }

When deserializing the whole class, I have a problem with property parameter 1. I see only default values.

i use ParameterConverter:

public class ParameterConverter: JsonConverter<Parameter>
     {
         public override ParameterRead(
             ref Utf8JsonReader reader,
             Type typeToConvert,
             JsonSerializerOptions options)
         {
             if (reader.TokenType == JsonTokenType.Null)
             {
                 return null;
             }
 
             Utf8JsonReader startReader = reader;
 
             using JsonDocument jsonDocument = JsonDocument.ParseValue(ref reader);
             JsonElement jsonObject = jsonDocument.RootElement;
             
             return JsonSerializer.Deserialize(ref startReader, typeof(FieldParameter)) as Parameter;
         }
 
         public override void Write(Utf8JsonWriter writer, Parameter value, JsonSerializerOptions options)
         {
             JsonSerializer.Serialize(writer, value, value.GetType());
         }
     }

but this Converter does not work. Why does the converter not see anything?

i expect to see {"fieldId": "SomeId","fieldType": "Field"}

i am use System.Text.Json.Serialization

more:
When i get string from jsonObject and i try manualy Deserialize, i see same result

string value = jsonObject.GetRawText();
var result2 = JsonSerializer.Deserialize<FieldParameter>(value)

.NET Version

5.0.15

[javiercn]

@psychomonkey9 thanks for contacting us.

This question is about how to use System.Text.Json and not related to ASP.NET Core. We are transferring the issue to the appropriate repo so that you can get a better and faster answer. In the meantime, we would suggest you check the following docs that cover this topic.

Tagging subscribers to this area: @dotnet/area-system-text-json, @gregsdennis
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

i have class:

public class SomeClass
    {
        public int Id { get; set; }
    
        public string Name { get; set; }
    
        [JsonConverter(typeof(ParameterConverter))]
        public Parameter parameter1{ get; set; }
    }
    
    public class Parameter
    {
       public ParameterType FieldType { get; set; }
    };
        
    public class FieldParameter : Parameter
    {
       public string FieldId { get; set; }
    }
    
    public enum ParameterType
    {
        Default,
        Field
    }

and this is example json:

{
      "id": 1,
      "name": "SomeName"
      "parameter1": {
        "fieldId": "SomeId",
  	  "fieldType": "Field"
      }
  }

When deserializing the whole class, I have a problem with property parameter 1. I see only default values.

i use ParameterConverter:

public class ParameterConverter: JsonConverter<Parameter>
     {
         public override ParameterRead(
             ref Utf8JsonReader reader,
             Type typeToConvert,
             JsonSerializerOptions options)
         {
             if (reader.TokenType == JsonTokenType.Null)
             {
                 return null;
             }
 
             Utf8JsonReader startReader = reader;
 
             using JsonDocument jsonDocument = JsonDocument.ParseValue(ref reader);
             JsonElement jsonObject = jsonDocument.RootElement;
             
             return JsonSerializer.Deserialize(ref startReader, typeof(FieldParameter)) as Parameter;
         }
 
         public override void Write(Utf8JsonWriter writer, Parameter value, JsonSerializerOptions options)
         {
             JsonSerializer.Serialize(writer, value, value.GetType());
         }
     }

but this Converter does not work. Why does the converter not see anything?

i expect to see {"fieldId": "SomeId","fieldType": "Field"}

i am use System.Text.Json.Serialization

more:
When i get string from jsonObject and i try manualy Deserialize, i see same result

string value = jsonObject.GetRawText();
var result2 = JsonSerializer.Deserialize<FieldParameter>(value)

.NET Version

5.0.15

Author:	psychomonkey9
Assignees:	-
Labels:	area-System.Text.Json
Milestone:	-

[eiriktsarpalis]

@psychomonkey9 your issue doesn't describe a standalone reproduction, but having reconstructed one based on your snippets I believe that your code has the following issues:

• There are casing mismatches between the class and JSON properties. For your example to work you need to pass a JsonSerializerOptions instance with PropertyNamingPolicy set to JsonNamingPolicy.CamelCase. More importantly, the options instances will need to be passed in the nested Deserialize call made inside your custom converter.
• In order for the FieldType property to be deserialized as expected, you need to specify JsonStringEnumConverter either on the property declaration itself or in the JsonSerializerOptions.Converter property.

Once I made these changes, my console app worked as expected:

using System;
using System.Text.Json;
using System.Text.Json.Serialization;

string json = @"
{
      ""id"": 1,
      ""name"": ""SomeName"",
      ""parameter1"": {
            ""fieldId"": ""SomeId"",
  	        ""fieldType"": ""Field""
      }
  }
";

var result = JsonSerializer.Deserialize<SomeClass>(json, options: new JsonSerializerOptions { PropertyNamingPolicy = JsonNamingPolicy.CamelCase });
Console.WriteLine(result);

public class SomeClass
{
    public int Id { get; set; }

    public string Name { get; set; }

    [JsonConverter(typeof(ParameterConverter))]
    public Parameter Parameter1 { get; set; }
}

public class Parameter
{
    [JsonConverter(typeof(JsonStringEnumConverter))]
    public ParameterType FieldType { get; set; }
};

public class FieldParameter : Parameter
{
    public string FieldId { get; set; }
}

public enum ParameterType
{
    Default,
    Field
}

public class ParameterConverter : JsonConverter<Parameter>
{
    public override Parameter? Read(
        ref Utf8JsonReader reader,
        Type typeToConvert,
        JsonSerializerOptions options)
    {
        if (reader.TokenType == JsonTokenType.Null)
        {
            return null;
        }

        Utf8JsonReader startReader = reader;

        using JsonDocument jsonDocument = JsonDocument.ParseValue(ref reader);
        JsonElement jsonObject = jsonDocument.RootElement;

        return JsonSerializer.Deserialize(ref startReader, typeof(FieldParameter), options) as Parameter;
    }

    public override void Write(Utf8JsonWriter writer, Parameter value, JsonSerializerOptions options)
    {
        JsonSerializer.Serialize(writer, value, value.GetType());
    }
}

It might be that you're experiencing something different, but in order for us to evaluate it properly, we would need to see a standalone reproduction like the one I shared above.

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