How can I check if a string is null or empty in PowerShell?

Question

Is there a built-in IsNullOrEmpty-like function in order to check if a string is null or empty, in PowerShell?

I could not find it so far and if there i

Answer 1

Note that the "if ($str)" and "IsNullOrEmpty" tests don't work comparably in all instances: an assignment of $str=0 produces false for both, and depending on intended program semantics, this could yield a surprise.