Adds an item into the cache, only if it does not already exist.

Declaration Syntax

Parameters
- key (String)
- The key of the item being added.
- item (Object)
- The item being added.
- expiry (TimeSpan)
- The interval after which the item expires and
is removed from the cache.
Assembly: Mindscape.LightSpeed (Module: Mindscape.LightSpeed) Version: 1.2.1393.0 (1.2.1393.0)