| WebExtension | Represents an Office Add-in instance. |
| WebExtensionBinding | Represents a binding relationship between an Office Add-in and the data in the document. |
| WebExtensionBindingCollection | Represents the list of binding relationships between an Office Add-in and the data in the document. |
| WebExtensionCollection | Represents the list of web extension. |
| WebExtensionProperty | Represents an Office Add-in custom property. |
| WebExtensionPropertyCollection | Represents the list of web extension properties. |
| WebExtensionReference | Represents identify the provider location and version of the extension. |
| WebExtensionReferenceCollection | Represents the list of web extension reference. |
| WebExtensionTaskPane | Represents a persisted taskpane object. |
| WebExtensionTaskPaneCollection | Represents the list of task pane. |