Problem with table in windows app

Question

I need change label tex with value index in my table after Press button. For example Press button, label.text = lap1, i Press again lap2 and next next to my limit in table.

What wrong?

void countlap()

{
int index = 0;
string[] lap = new string[5] { "lap 1", "lap 2", "lap 3", "4", "5", };

if ( index < lap.Length)
{ index++; };

labelbieg.Text=(lap[index]);

}