# IProgressNotify

The IProgressNotify interface enables applications and other objects to receive notifications of changes in the progress of a downloading operation.

##### When to Implement

You do not need to implement IProgressNotify. The downloading code implements this interface, and the asynchronous storage implementation provides a connection point for dispatching notifications to it. An application can also register an IProgressNotify sink to receive progress notifications for individual streams.

##### When to Use

You do not need to call this interface. The Compound Files implementation uses IProgressNotify::OnProgress to control the blocking behavior of the asynchronous storage and to trigger additional byte range requests if applicable.

Methods in VTable Order

IUnknown Methods | Description
QueryInterface | Returns pointers to supported interfaces.
AddRef | Increments reference count.
Release | Decrements reference count.

IProgressNotify Method | Description
OnProgress | Receives status information about progress of download operation.