netcoreapp3.0 
namespace System.Text.Json
{
    public enum JsonValueType : byte
    {
        Undefined = 0
    }
}
.NET
5.06.07.08.09.010.011.0
.NET Core
3.03.1
Information specific to netcoreapp3.0
Assembly

System.Text.Json , Version=4.0.0.0, PublicKeyToken=cc7b13ffcd2ddd51

Referencing

Your project needs a package reference to Microsoft.AspNetCore.App.

Package Microsoft.AspNetCore.App (3.0.0-preview3-19153-02) netcoreapp3.0
Preview This API is contained in a prerelease package.
Platform Restrictions

This framework does not have platform annotations.

  • Built-in API
  • Package-provided API