control cannot fall through from one case label ('default:') to another

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C#

private void PlaceRandom()
{
int r, c;
r = 10; c = 10;
int i = 0;
ar = 0;
ac = 0;
Random rnd = new Random();
int val;
while (i < 8)
{
val = rnd.Next(9);
if (numNotExists(val) == true && val > 0)
{
pos[ar, ac] = val;

switch (val)
{
case 1:
lbl1.Location = new Point(c, r);

break;
case 2:
lbl2.Location = new Point(c, r);

break;
case 3:
lbl3.Location = new Point(c, r);

break;
case 4:
lbl4.Location = new Point(c, r);

break;
case 5:
lbl5.Location = new Point(c, r);

break;
case 6:
lbl6.Location = new Point(c, r);

break;
case 7:
lbl7.Location = new Point(c, r);

break;
case 8:
lbl8.Location = new Point(c, r);

break;
default:

}
c += 100;
ac++;
if (ac > 2)
{
ac = 0;
ar++;
}
if (c > 300)
{
c = 10;
r += 100;
}
i++;
}
else
continue;
}
lblBlank.Location = new Point(c, r);
pos[2, 2] = 9;
}




it showing an error "control cannot fall through from one case label ('default:') to another" at the default statement of the switch case i cant understand why
and what could be the reson