Why would you use a ".pfx" file in .NET

Question

What is the ".pfx" extension used for in .NET?

Why does it ask for a password when the solution is being built?

Answer 1

A file containing an encrypted private key. It's probably being used for code signing the application (so the user knows who created the program and hence if they can trust it).

You can probably see it being used by right-clicking on the project, getting Properties, then looking at the Signing tab.