The System.Runtime.Serialization.ObjectIDGenerator keeps track of previously identified objects. When you ask for the ID of an object, the System.Runtime.Serialization.ObjectIDGenerator knows whether to return the existing ID, or generate and remember a new ID.

The IDs are unique for the life of the System.Runtime.Serialization.ObjectIDGenerator instance. Generally, a System.Runtime.Serialization.ObjectIDGenerator life lasts as long as the System.Runtime.Serialization.Formatter that created it. Object IDs have meaning only within a given serialized stream, and are used for tracking which objects have references to others within the serialized object graph.

Using a hash table, the System.Runtime.Serialization.ObjectIDGenerator retains which ID is assigned to which object. The object references, which uniquely identify each object, are addresses in the runtime garbage-collected heap. Object reference values can change during serialization, but the table is updated automatically so the information is correct.

Object IDs are 64-bit numbers. Allocation starts from one, so zero is never a valid object ID. A formatter can choose a zero value to represent an object reference whose value is null.

Namespace: System.Runtime.Serialization
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0, 4.0.0.0