C# parser reads "$" as "Interpolated string expression" which is not correct

[Khaos66]

Describe the bug
With this C# code the method is not recognized correctly

namespace Sample.NS
{
    public class MyClass
    {
        Regex pattern = new(@".$");

        public void Fu() { }
    }
}

Expected behavior
In readme.md I need to use @ref Sample.NS.MyClass.Fu as a reference

To Reproduce
DoxygenSample.zip
In this sample the method before the ".$" string is recognized, but the second method after it is not.

Version
doxygen 1.9.6 has this issue

[Khaos66]

@albert-github I hope the issue is setup correctly

[albert-github]

I've just pushed a proposed patch, pull request #9847

[albert-github]

Code has been integrated in master on GitHub (please don't close the issue as this will be done at the moment of an official release).

[doxygen]

This issue was previously marked 'fixed but not released',
which means it should be fixed in doxygen version 1.9.7.
Please verify if this is indeed the case. Reopen the
issue if you think it is not fixed and please include any additional information
that you think can be relevant (preferably in the form of a self-contained example).