I want to develop addins for Office (Outlook,Word and Excel). The code will be almost the same. The difference is only for retrieve a document (mail for Outlook, document for Word,graphic/chart for Excel.
Should I develop 3 addins and therefore I will have 3 installations for my users. Or can I develop only 1 addin and add a condition somewhere?
Best How To :
Yes, that is possible. You possibly need 3 different
AddIn classes, since every platform has it's own format and parameters and you might want to deviate some logic, though there is nothing to stop you integrating the three add-ins in one.
Another option is to make a class library that only uses the general Office assembly, and include that library into your other projects.
For the deployment: you can't use ClickOnce out of the box for that, since ClickOnce only supports a single Office program per installation. You can tweak the installation though, as explained on this article on MSDN: Deploying Multiple Office 2010 Projects in One Package.