Manually destroy C# objects

Question

I am fairly new to learning C# (from Java & C++ background) and I have a question about manual garbage disposal: is it even possible to manually destroy an object in C#?

Answer 1

Although you can trigger garbage collection (you need to trigger GC for all generations because you can't be sure which generation the finalizable object is in) you cannot necessarily force finalization of a particular object. You can only depend upon assumptions about how the garbage collector works.

Furtnermore, since finalization happens on its own thread, you should call WaitForPendingFinalizers after triggering garbage collection.

GC.Collect(GC.MaxGeneration);
GC.WaitForPendingFinalizers();

As was noted by others, this can actually hurt your application's performance because unnecessarily invoking the GC can promote otherwise short-lived objects into higher generations which are more expensive to collect and are collected less frequently.

Generally speaking, a class that implements a finalizer (destructor) and does not implement IDisposable is frowned upon. And anything that implements IDisposable should be calling it's finalizer logic and supressing itself from finalization at garbage collection.

Jeff Richter recently posted a nice little trick for receiving a notification when garbage collection occurs.

Another great article on Garbage Collector Basics and Performance Hints by Rico Mariani (MSFT)

Answer 2

It's not possible to destroy an object in a deterministic fashion. The CLR determines when the flagged object is reclaimed. This means that while you can flag an object for reclamation and ensure that managed and unmanaged resources are tidied up for disposal (by implementing the IDisposable pattern), the actual time the memory is released is up to the CLR. This is different from C++ where you could actually delete something and it would be released then.