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The Role of Application Roots

Now, back to the topic of how the garbage collector determines when an object is “no longer

needed.” To understand the details, you need to be aware of the notion of 

application roots. Simply

put, a 

root is a storage location containing a reference to an object on the heap. Strictly speaking, a

root can fall into any of the following categories:

• References to global objects (while not allowed in C#, CIL code does permit allocation of

global objects)

• References to any static objects/static fields

• References to local objects within an application’s code base

• References to object parameters passed into a method

• References to objects waiting to be 

finalized (described later in this chapter)

• Any CPU register that references an object

During a garbage collection process, the runtime will investigate objects on the managed heap

to determine whether they are still reachable (aka 

rooted) by the application. To do so, the CLR will

build an object graph, which represents each reachable object on the heap. Object graphs will be

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