Vsto 4.0

At its core, VSTO 4.0 (introduced with Visual Studio 2010) is a runtime that allows developers to write C# or VB.NET code that lives directly inside Office applications. Unlike the modern JavaScript API, VSTO has "god mode" access:

While the landscape of Office development has shifted significantly in recent years with the introduction of the JavaScript-based Office Add-ins model, (Visual Studio Tools for Office) remains a critical technology for the business world. vsto 4.0