Question

Is it possible to create a portable VSTO application ? (e.g without setup.exe, without admin rights, without clickonce, etc.)

Answer 1

Any vsto solution requires that:

• The .net framework is installed on the target machine
• The VSTO runtime is installed on the target machine

If you don’t have those installed already the answer to your question is: No

If you define those as prerequisites then there are 2 kind of vsto solutions. It can be either a document based solution or an office add-in.

• Document based solutions have the assemblies along side of the document and get automatically loaded with the excel file. There is no seperate setup required so you could call those ‘portable’ (depending on what your prereqs are).
• Real office add-ins require registry keys to be created. I don’t think there is any way you could get those running without some sort of setup/install procedure

For more information about document level solutions and how they are dealt with on runtime look here