.NET 8 – Include non-public members in JSON serialization

Starting with .NET 8 you can include non-public properties in the serialization when using System.Text.Json. To do so, simply decorate the non-public property with the JsonIncludeAttribute attribute.

[System.AttributeUsage(System.AttributeTargets.Field | System.AttributeTargets.Property, AllowMultiple=false)]
public sealed class JsonIncludeAttribute : System.Text.Json.Serialization.JsonAttribute

The attribute works with any non-public modifier, such as private, protected or internal. Let’s look at an example:

string json = JsonSerializer.Serialize(new MyClass(1, 2, 3));

Console.WriteLine(json);

public class MyClass
{
    public MyClass(int privateProperty, int protectedProperty, int internalProperty)
    {
        PrivateProperty = privateProperty;
        ProtectedProperty = protectedProperty;
        InternalProperty = internalProperty;
    }

    [JsonInclude]
    private int PrivateProperty { get; }

    [JsonInclude]
    protected int ProtectedProperty { get; }

    [JsonInclude]
    internal int InternalProperty { get; }
}

As expected, this will output the following:

{"PrivateProperty":1,"ProtectedProperty":2,"InternalProperty":3}