# Compound Document Interfaces

The following tables list the interfaces implemented by OLE containers, OLE servers, and compound document objects. The required interfaces must be implemented on the components for which they are listed. For example, containers must implement the IOleClientSite and IAdviseSink interfaces. All other features are optional. If you want to include a particular feature in your application, however, you must implement the interfaces shown for that feature in the table below. All other interfaces are required only if you are including a particular feature. For example, if you want your application to do message filtering (recommended), you must implement IMessageFilter.

The following table lists required and optional behaviors for OLE containers and which interfaces you must implement for each.

OLE Containers

Behavior | Interfaces
Required Behaviors | IOleClientSite
| IAdviseSink
Message Filtering | IMessageFilter
Linking | none
Linking to Embedded Objects | IOleItemContainer
| IPersistFile
| IClassFactory
In-Place Activation | IOleInPlaceSite
| IOleInPlaceActive-Frame
| IOleInPlaceUIObject
Drag and Drop | IDropSource
| IDropTarget
| IDataObject

The following table lists required and optional behaviors for OLE servers and their compound document objects and which interfaces you must implement for each. The table distinguishes OLE servers and their objects in order to clarify which component implements which interfaces. The table also notes the different requirements of objects provided by out-of-process versus in-process servers.

Feature | OLE Server | Compound Document Object |
|  | Out-of-Process | In-Process
Required Behaviors | IClassFactory | IOleObject | IOleObject
|  | IDataObject | IDataObject
|  | IPersistStorage | IPersistStorage
|  |  | IViewObject2
|  |  | IOleCache2
Message Filtering | IMessageFilter |  |
Linking | IOleItemContainer |  | IOleLink
| IPersistFile |  | IExternalConnection
In-Place- Activation |  | IOleInPlaceObject | IOleInPlaceObject
|  | IOleInPlace- ActiveObject | IOleInPlaceActive- Object
Drag and Drop | IDropSource |  |
| IDropTarget |  |
| IDataObject |  |