title: .NET Core MarshalByRefObject equivalent
body: <p>Is there an equivalent of the <a href="https://msdn.microsoft.com/fr-fr/library/system.marshalbyrefobject(v=vs.110).aspx" rel="nofollow noreferrer"><code>MarshalByRefObject</code></a> class for .NET Core?</p>
  
  <p>I need a reference type that can be used as a identifier. The identifier have to be a reference type because I need to map a list of identifiers to a list of instances in a <a href="https://msdn.microsoft.com/en-us/library/dd287757(v=vs.110).aspx" rel="nofollow noreferrer"><code>ConditionalWeakTable</code></a> that only accept reference types as key. A <a href="https://msdn.microsoft.com/fr-fr/library/dd287191(v=vs.110).aspx" rel="nofollow noreferrer"><code>ConcurrentDictionary</code></a> can't be used in my case, so I can't use something like a GUID.</p>
  
  <p>I have to reproduce this piece of code <a href="https://github.com/ninety7/DbContextScope/blob/master/src/DbContextScope.EfCore/Implementations/DbContextScope.cs" rel="nofollow noreferrer">https://github.com/ninety7/DbContextScope/blob/master/src/DbContextScope.EfCore/Implementations/DbContextScope.cs</a>.</p>