#929 – Visualizing How Objects Are Removed from the Managed Heap

Suppose that you create two Dog objects as follows.  (The BestFriend property refers to another dog that is the first dog’s best friend).

            Dog myDog = new Dog("Kirby", 15);
            myDog.BestFriend = new Dog("Jack", 17);

The managed heap now looks as follows:

Now suppose that you then execute the following lines of code:

            Dog yourDog = new Dog("Bowser", 3);
            yourDog = new Dog("Hank", 5);

Now the managed heap looks as follows:

At this point, let’s assume that the Garbage Collector runs, in an effort to reclaim some memory. Notice that the Bowser object is no longer referenced by any reference-typed variable or by another object. Bowser gets marked for collection:

All objects not marked for collection are compacted, moving them to the front (left) of the heap.  After the Garbage Collector runs, the heap is as shown below.  Note that the memory for the Bowser object is reclaimed by the heap.

#927 – Visualizing How Objects Are Created on the Managed Heap

Suppose that you create a couple of new objects and refer to them using referenced-typed variables, as follows:

            Dog myDog = new Dog("Kirby", 15);
            Dog yourDog = new Dog("Bowser", 3);

You now have two variables of type Dog, each referring to an instance of a Dog object.  The Dog objects exist on the managed heap.

Suppose that you now change the yourDog variable to also reference the “Kirby” dog, as follows:

            yourDog = myDog;

The managed heap still contains the two original Dog objects. But notice that the “Bowser” dog is no longer currently referenced by any reference-typed variables.  Bowser is no longer reachable from any of the reference-typed variables, but this Dog object has not yet been destructed, or its memory reclaimed.

#925 – The Managed Heap

The managed heap is an area of the virtual memory available to your process that the Common Language Runtime (CLR) uses for storing instances of reference types (objects) that you create.  The Garbage Collector (GC) is the component in the CLR that is reponsible for allocating memory on the heap for your objects and for releasing that memory when the objects are no longer referenced.