Replace an existing object with a new one in the same place in memory

Question

In C# it is possible to pool existing objects in an ObjectPool. But this only works for reference types that provide a method to reset the object to some well defined initial state. For example a type may implement IResettable interface or provide a method that mirrors its constructor.

I wonder if it would be possible to pool any arbitrary reference type. The steps would be the following:

• Call ObjectPool<T>.Get() to get an instance.
• Replace the memory pointed to by the recovered instance with a new fresh instance.
• Use the new object and return it to the pool when done.

The question is if it is at all possible to achieve point 2. Theoretically it should be possible. I am, however, not sure if it is possible in C#. From what I understand the new keyword will always create an instance at an unoccupied "slot" in the managed heap. What would be needed for this to work is a way to create a new object at a specified memory location. Furthermore, one would need to make sure that the old object was disposed of, hoping that disposal is enough and call to the finalizer is not needed.

Answer 1

Only way to achieve that is to let the user of the pool get a PoolElement<T> instead of a instance of T. And make sure he access the instance through the PoolElement. Which you cant guarantee.

I wouldn't recommend this approach.

There are better ways, pub/sub for example.