C# Regex.replace Pattern needed

Question

Usually I make my Regex patterns by myself, but I can't figure this one out:
I need a Regex.Replace that replaces "'Number'/'Number'" to "'Number'von'Number'".

Example: "2/5" schould become "2von5".

The problem is that I can't just replace "/" to "von" because there are other "/" that are needed.

Answer 1

You can replace (?<=\d)/(?=\d) with von, using lookaround.

Another option is to replace (\d)/(\d) with $1von$2 (though that would fail on 1/2/3).