Check if a variable is in an ad-hoc list of values

Question

Is there a shorter way of writing something like this:

if(x==1 || x==2 || x==3) // do something

What I'm looking for is something like this:

if(x.in((1,2,3)) // do something

Answer 1

I'm entirely guessing here, correct the code if I'm wrong:

(new int[]{1,2,3}).IndexOf(x)>-1