What causes "unresolvable conflict(s)" when renaming in Visual Studio 2015?

Question

I get an error that there are "unresolvable conflict(s)" when renaming certain identifiers in Visual Studio. What's causing this?

Answer 1

The file was a temporary file opened from source control, not part of the solution. I assume Visual Studio was unable to determine all instances of the identifier from just the isolated file. Renaming the method in the actual project file succeeded with no issues.