Extension Manager - a singleton.
The ExtensionManager is designed to allow you to enable licensed extensions, such as ArcGIS 3D Analyst, within your standalone application.
Being a singleton object, ExtensionManager is the one and only instance of its class. An application can have only one ExtensionManager object. You could cocreate and use ExtensionManager from within ArcMap, but there is no real need as the IExtensionManager interface is also available on the Application object.
See the About Extensions topics for more details.
Extended Error Information
Use the ISupportErrorInfo method InterfaceSupportsErrorInfo to determine if the object supports extended error information. If the object supports extended error info, VC++ developers should use the OLE/COM IErrorInfo interface to access the ErrorInfo object. Visual Basic developers should use the global error object Err to retrieve this extended error information.
|IExtensionManager||Provides access to members that query extension.|
|IExtensionManagerAdmin||Provides access to members that give life to the extensions.|
|IJITExtensionManager||Provides access to the Just In Time Extension Manager.|
|ISupportErrorInfo (esriSystem)||Indicates whether a specific interface can return Automation error objects.|
If you are building an application that makes use of licensed extension functionality like ArcGIS Spatial Analyst, ArcGIS 3D Analyst, or ArcPress for ArcGIS, you need to take responsibility for enabling the extension you're using.
The ExtensionManager was designed for this purpose. The model is that you create the ExtensionManager and hold onto it for the life of your application. Before you use a licensed extension, you need to load it and enable it. You load the extension using IExtensionManagerAdmin::AddExtension and passing in the CLSID of the extension. Then before you use the extension, you need to enable it.
To enable the extension, find the extension using IExtensionManager::FindExtension , QI for IExtensionConfig on the extension, and then set the State property to esriESEnabled. Keep in mind that setting this property may fail, so be prepared to handle that in your application. If enabling the extension succeeds, that means that the license was checked out. If not, then the license could not be acquired.
If during the life of your application, you want to give the license back, simply set the state to esriESDisabled. If that succeeds the license was checked back in. If it failed that means there are outstanding objects (from the extension) that are still using the license.