Well, there's a lot wrong, really.
Originally Posted by DecenyDefied
You're calling the method totally wrong.
That makes no sense, and I'm surprised it even compiles, if it does.
static void Main()
Your method name is selectionSort. You need to call Program.selectionSort() (you declared it static), but it appears to take arguments, so you'd need to pass those as well.
I'm not totally sure what the arguments are FOR, though. If you pass something called size, I'd imagine you meant to set an array size dynamically and use it in that loop like you do. But you hard-coded it to 10 and at the moment size is undefined because you aren't passing the value.
There's more wrong here than right, honestly. You may want to re-read your class material and ask for help from your instructor.