Under the Hood of .NET Memory Management - Simple Talk

Chapter 1: Prelude
When an Order is added to the order collection, the collection itself then holds a
reference to the added order. If the instance of the Customer class had a stack reference
to it as well, it would have the following references:
• a stack-based root reference for a Customer containing:
• a reference to the orders ArrayList collection, which contains:
• references to order objects.
Figure 1.6: Reference tree for a typical scenario.
Figure 1.6 shows the basic reference tree, with a global root reference to a Customer class
that, in turn, holds a collection of Order classes.
This is important because if an object doesn't ultimately have a root reference then it
can't actually be accessed by code, so it is no longer in use, and can be removed. As you
can see above, a large number of objects can be maintained by just a single root reference,
which is both good and bad, as we'll see later.
Inspection and collection
To make sure objects which are no longer in use are cleared away, the GC simply gets a
list of all root references and, for each one, moves along its reference tree "marking" each
object found as being in use (we'll come back to what that means in just a moment). Any
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