There are some funny things you might need to do when you are calling a class in another namespace from your office addin, i.e doing an interop.
- Firstly you need to have a Guid for identifiying the interop class. This apparently is used for registering this class as an interop in the registry
- Secondly you need to set a property at the project level in VS.net, "Register for COM interop = true".
- If you are using an installer , the you need to make sure that in the properties of this project , you have the property "Register" set to "vsdraCOM".
If that is not enough, if you do not do any of the above, you do not get any pretty error messages that tell you to do so. Your addin might just stop working all of a sudden or will work on one box and stop working on the other. Hmpf!!
To add to all this, the documentation for COM is really pathetic , even in MSDN. The best resource for you are blogs of those unfortunate developers , who have suffered the pain and agony of working with Microsoft components