Description

Calling string.Normalize(form) or IsNormalized(form) on an ASCII string when form is a compatibility form (i.e. FormKD or FormKC) does not throw - it only throws if the string is not ASCII. I find this behavior to be a little bit troubling - I think it should always throw for the unsupported form instead of giving false hope that it works. The current behavior can make it look like code paths work and then you get PlatformNotSupportedException at runtime after deployment when users enter a non-ASCII string.

Reproduction Steps

"asdf".IsNormalized(NormalizationForm.FormKD); // no throw
"😊".IsNormalized(NormalizationForm.FormKD); // throws

Expected behavior

Should always throw when requesting an unsupported form.

Regression?

No

Known Workarounds

No response

Configuration

No response

Other information

No response