Question 109738 in Json Question posted in
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What is System.Text.Json equivalent for XmlElment(name, type)

I have the following class.

public class Foo
{
    [XmlElement("Bar", typeof(Bar))]
    [XmlElement("Pub", typeof(Pub))]
    public BaseBar Bar { get; set; }
}

I would like to move from XML serialization to JSON (System.Text.Json) serialization, what is the equivalent for the attribute [XmlElement("Bar", typeof(Bar))]?

See this sample: https://dotnetfiddle.net/pU8QAU

Edit:

I am looking for a way to define it on property level, so if I have 2 properties I would like to have different names for those.

public class Foo
{
    [XmlElement("Bar", typeof(Bar))]
    [XmlElement("Pub", typeof(Pub))]
    public BaseBar Bar { get; set; }

    [XmlElement("Bar2", typeof(Bar))]
    [XmlElement("Pub2", typeof(Pub))]
    public BaseBar Bar2 { get; set; }
}

See this sample: https://dotnetfiddle.net/M6nla

Edit2:

The given answer by Guru Stron produces this output

{"Bar":{"$type":"Pub" …

I am looking for

{"Pub":{…

Where Pub should be serialized from the property Bar if it is of type Pub.

Tags:

2

Answers


  1. 0

    .NET 7 and latest version of System.Text.Json have introduced support for polymorphic json serialization. One way to handle it is to use JsonDerivedTypeAttribute on the base type specifying all descendants:

    [JsonDerivedType(typeof(Bar), typeDiscriminator: nameof(Bar))]
[JsonDerivedType(typeof(Pub), typeDiscriminator: nameof(Pub))]
public abstract class BaseBar
{
    public abstract string Text { get; set; }
}

public class Bar : BaseBar
{
    public override string Text { get; set; } = "I am a Bar";
}

public class Pub : BaseBar
{
    public override string Text { get; set; } = "I am a Pub";
}

    Prior .NET 7 custom converter could be used to support polymorphic deserialization.

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  2. 0

    To serialize you data, you even don’t need any element name attribute, if you have the same property name and you don’t need a root class, you can use a Dictionary

        var foo = new Dictionary<string, BaseBar> {
                           { "Bar", new Bar() },
                           { "Pub", new Pub() }
                           };

    var json = System.Text.Json.JsonSerializer.Serialize(foo, 
                                new JsonSerializerOptions{WriteIndented = true}
                                );

    output

    {
  "Bar": {
    "Text": "I am a Bar"
  },
  "Pub": {
    "Text": "I am a Pub"
  }
}

    to deserialize

    Dictionary<string, BaseBar> foo = JsonObject.Parse(json).AsObject()
                                    .ToDictionary(p => p.Key, p => p.Key == "Bar" ? 
                                      (BaseBar)p.Value.Deserialize<Bar>()
                                    : (BaseBar)p.Value.Deserialize<Pub>()
                                    );
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