ArcObjects Library Reference  (NetworkAnalyst)    

NamedSet CoClass

A collection class with access to the items by index or name.

Product Availability

Available with ArcGIS Engine, ArcGIS Desktop, and ArcGIS Server. Requires Network Analyst Extension.

Interfaces

Interfaces Description
INamedSet Provides access to a collection of named items.
IPersistStream (esriSystem)

Remarks

The NamedSet class is a collection of name value pairs. The name must be a string, but the value can be used to store items such as strings, numbers, dates, or even interface pointers to objects.

A NamedSet is similar to a PropertySet in that they both store a collection of objects that can be retrieved by an associated name.  The difference is how the objects are accessed.