The CLR provides each AppDomain with a GC Handle Table that lets applications monitor or explicitly control object lifetimes. The table is empty when the AppDomain is created.

Each entry contains:

• A reference to an object on the managed heap
• A flag describing how to monitor/control that object

You typically interact with this via System.Runtime.InteropServices.GCHandle (e.g., GCHandleType.Weak, WeakTrackResurrection, Normal, Pinned). Use cases include pinning objects for interop or creating weak references without allocating WeakReference.

Example (pinning):

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var bytes = new byte[1024];
var handle = GCHandle.Alloc(bytes, GCHandleType.Pinned);
try
{
    IntPtr ptr = handle.AddrOfPinnedObject();
    // pass ptr to native API
}
finally
{
    handle.Free();
}

Example (weak):

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var target = new object();
var handle = GCHandle.Alloc(target, GCHandleType.Weak);
target = null;
GC.Collect();
var alive = handle.Target != null; // may be null after collection
handle.Free();

Prefer high-level WeakReference unless you specifically need GCHandle semantics (e.g., pinning or resurrection tracking). Always Free() to avoid leaks.