Even though C# and others are listed as a possible language, all of the samples I have found show how to create a task pane AddIn using HTML5/JavaScript only.
I've already gone through all of these:
- How to: Create your first task pane app by using "Napa" Office 365 Development Tools
- How to: Create a basic app for SharePoint by using "Napa" Office 365 Development Tools
- How to: Create your first mail app for Outlook by using "Napa" Office 365 Development Tools
- How to: Create your first content app for Excel by using "Napa" Office 365 Development Tools
and others, and they are all HTML5/JavaScript! Even the MSDN samples are HTML5/JavaScript only!
How can I have an ASP.NET Web Application talk to Office 365 so it can provide a task pane control and edit the selected text?