Applies to:

By providing a Component Object Model (COM) Interop layer and COM Interop tools, Microsoft has made the transition of applications from the COM world to the .NET world as seamless as possible. You can implement COM (unmanaged) interfaces in .NET (managed code) and use those implementations transparently from COM-based clients.

If you want to build custom managed COM add-ins in Microsoft� Office XP, there are three interfaces that would be of special interest to you: the IDTExtensibility2, IsmartTagRecognizer, and ISmartTagAction interfaces. The IDTExtensibility2 interface is implemented when building custom COM add-ins, and the ISmartTagRecognizer and ISmartTagAction interfaces are implemented when building custom smart tag COM add-ins.

In this article we will discuss the installation and deployment of managed COM add-ins in Office XP. Unless otherwise indicated, we will use the term COM add-ins to mean COM add-ins that implement the IDTExtensibility2, IsmartTagRecognizer, or ISmartTagAction interfaces. It will be obvious from the context of a sentence when we make a distinct differentiation between smart tag COM add-ins and COM add-ins that only implement the IDTExtensibility2 interface.

When a managed COM add-in is deployed using the register assembly (regasm) utility and the security setting in an Office XP application is set to Medium with Trust all installed add-ins and templates disabled, the user will be prompted to either enable or disable the COM add-in when the application is launched. However, if the security level is set to High with Trust all installed add-ins and templates disabled, your managed COM add-in won't be loaded even when it is signed.