Why doesn't the "quot; string operator work in this interpreter/environment?

Answer 1

Because string interpolation is only available in C# 6 onwards which is not supported by SoloLearn's cloud compiler, yet. 😉

Answer 2

Is that true ?
It have use it in this code

https://code.sololearn.com/cAiNdtyF9cPg

the $-sign means that variable can be use inline like {cats}
instead of using place holders like {0}

https://www.dotnetperls.com/string-interpolation