DynamoVisualProgramming.DynamoServices by Autodesk

<PackageReference Include="DynamoVisualProgramming.DynamoServices" Version="2.16.2.5524" />

 KeepReferenceThisAttribute

This attribute is applied to member function of zero touch libary. It indicates the return object should keep a reference to "this" object so that even "this" object is out of scope, it will not be disposed. Note the type of return object should be reference type, either a pointer or an array.
using System; namespace Autodesk.DesignScript.Runtime { [AttributeUsage(AttributeTargets.Method)] public class KeepReferenceThisAttribute : Attribute { } }