ReSharper Curiosity: “Parameter is only used for precondition check(s).”

It’s not judging, it’s trying to help 🙂

If ReSharper sees that a parameter is only used as a check to throw an exception, it greys it out, indicating that you’re not actually using it for “real” work. This is most likely a mistake – why pass in a parameter you’re not going to use? It usually indicates that you’ve used it in a pre-condition, but then forgotten (or no longer need) to use it elsewhere in the code.

Since the method is an assertion method (that is, all it does is assert it’s valid), you can suppress the message by marking the ValidateCorrespondingValueType as an assertion method, using ReSharper’s annotation attributes, specifically the [AssertionMethod] attribute:

[AssertionMethod]
private void ValidateCorrespondingValueType(SupportedType supportedType, object settingValue)
{
  // …
}