If you found a "Visual Studio 2015 Portable" download online, it's almost certainly , a cracked version (illegal), or a fake . Microsoft does not release portable versions of full Visual Studio IDEs.
refers to a non-standard version of Microsoft's flagship Integrated Development Environment (IDE) that is modified to run directly from a USB drive or local folder without a permanent installation. Visual Studio 2015 Portable
If you truly need a portable development environment for Windows C++/C# with VS2015 compatibility: If you found a "Visual Studio 2015 Portable"
To directly answer the original query: Microsoft never intended for it to be portable, and the technical obstacles (registry, GAC, services) make a clean portable version impossible. it's almost certainly