Exceptions and Errors are the same things. Somewhere in software history, someone came up with the phrase “Exceptions are exceptional”. That sounds catchy but it doesn’t translate to Exceptions and Errors. If you go that route then who decides what is Exceptional? It is very subjective because an error for one context could be exceptional to one and not to another. Exceptional and Exception are very different words. Someone apparently thought the catchy phrase enforces the idea that there is a difference.

They are the same thing. I’m not a Java developer and I realize it has different classes for each but in the .NET world they are the same thing. The preferred error handling framework in .NET is the Exception class. It doesn’t care what you want to call it, an error or an exception. Nor does it care if it is exceptional or not. It is just a vehicle for communicating error information. You can communicate the severity of an error by creating and using classes that inherit from Exception.

To clarify, I’m speaking about the .NET library level, not the HTTP API level. I fully agree with the majority that data validation should not be considered an exception. Data validation should be handled before you get to the library level. There are many libraries available to make data validation cleaner and easier to use. Note that underneath, those libraries are throwing errors.

The Source of my information is here:

Cwalina, K., Abrams, B. F., Barton, J., Icaza, M. de, & Hejlsberg, A. (2020). Framework design guidelines: Conventions, idioms, and patterns for reusable .net libraries. Addison-Wesley.