A POS Client .NET Extension Application is a .NET class library that adds new operations or event handlers to the Simphony POS client.
An Extension Application adds new operations by defining extension methods that are invoked using buttons created in the Page Designer module. Existing operations are extended by implementing event handlers for POS client events. Extension methods and event handlers are able to interact with the POS client using the Extension Application API.
The POS Client Extension Application API is the set of data types used by the Extension Application to interact with the POS client; this interaction includes the ability to add items to a guest check, prompt the user for information, invoke existing operations, evaluate configuration elements (such as employee options), and more.