Visual Studio Addin project templates
If you want to create a Visio add-in, there are several options available. You can go with plain COM addin, VSTO (Visual Studio Tools for Office) addin, or with a VSL. This project template provides an improved starting point to build managed Visio addins with Visual studio (including free Visual Studio Community Edition ).
Link to download from Visual Studio Gallery
What the addin project provi...