<PackageReference Include="System.Runtime.Serialization.Formatters" Version="11.0.0-preview.3.26207.106" />

System.Runtime.Serialization.ObjectIDGenerator

public class ObjectIDGenerator
Generates IDs for objects.
namespace System.Runtime.Serialization { public class ObjectIDGenerator { public ObjectIDGenerator(); public virtual long GetId(object obj, out bool firstTime); public virtual long HasId(object obj, out bool firstTime); } }