Differences between Visual Studio 2010 add-in manager and extension manager

The difference between开发者_JAVA技巧 Add-In and Integration Package is still unclear and now with Visual Studio 2010 an extension manager appears along with the add-in manager.

• What are the differences between the add-in manager and the extension manager?
• Can an add-in be in both manager at the same time?

Add-ins implement an extensibility interface that was first created for Visual Studio.Net for customizing and automating the IDE. These add-ins are supported in Visual Studio 2002/2003/2005/2008/2010.

Extensions are MEF components and do not normally implement the Add-in interface. Visual Studio 2010 is the first version of Visual Studio to support MEF components.

Only Add-ins appear in the Add-in Manager. Only Extensions appear in the Extension Manager.

I don't know if an MEF extension could also be loaded by Visual Studio as an add-in, but there's really not much reason that to happen. An extension can use the add-in DTE interfaces without actually being loaded as an add-in.