How to Implement a Custom JsonConverter in JSON.NET for Polymorphic Deserialization?

Json.net customizes JSONCONVERTER to process polymorphic derivativeization

When dealing with polymorphic types in JSON.NET, when the type is not clearly defined in JSON, the JSON data back -sequentialization backbone type object may be challenging. This guide demonstrates how to achieve custom JSONCONVERRER to overcome this obstacle.

Challenge

Consider the following JSON data:

The task is to return this JSON data to

, where

[
  {
    "Department": "Department1",
    "JobTitle": "JobTitle1",
    "FirstName": "FirstName1",
    "LastName": "LastName1"
  },
  {
    "Department": "Department2",
    "JobTitle": "JobTitle2",
    "FirstName": "FirstName2",
    "LastName": "LastName2"
  },
  {
    "Skill": "Painter",
    "FirstName": "FirstName3",
    "LastName": "LastName3"
  }
]

is the base class, and

and List<Person> are derived classes. Person Employee <决> Solution Artist

In order to deal with this situation, we will create a custom class called , which inherits

.

Class is a custom converter used when the type of the values ​​that infer the values ​​of the back -sequentialization from the JSON data. PersonConverter JsonConverter Personconverter Implement JsonCreationConverter<Person> JsonCreationConverter<T>

Readjson method rewriting

In our custom

public class PersonConverter : JsonCreationConverter<Person>
{
    protected override Person Create(Type objectType, JObject jObject)
    {
        if (FieldExists("Skill", jObject))
        {
            return new Artist();
        }
        else if (FieldExists("Department", jObject))
        {
            return new Employee();
        }
        else
        {
            return new Person();
        }
    }

    private bool FieldExists(string fieldName, JObject jObject)
    {
        return jObject[fieldName] != null;
    }
}

, the

method is rewritten to perform the following steps:

Read JSON data into

. PersonConverter ReadJson Call the method to determine the type according to the JSON attribute.

Use the method to fill the attribute of the object.
1. JObject Back to the newly created object.
2. Create Use the converter
3. JsonSerializer.Populate To use a custom converter, you can use the following code:
Conclusion

By achieving custom , you can handle polymorphic derivatives in json.net. The provided in this guide demonstrates how to analyze JSON data and determine the appropriate derived type. This method can flexibly handle polymorphism during the deepertine.

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