if skips straight to else C#

On the click of a button, I store the user's textbox input into an int variable "rc". After that I declared an if statement like this:

 if (rc == 3 || rc == 5 || rc == 7 || rc == 9 || rc == 11)
{//things I want it to do.} else {//do this...}

the problem is, that even if the user does enter a 3 or 5 or 7 or any of those options, it will just skip to else and show the MessageBox that comes with it. Why could this be? Here's a look at my code, ANY help would be appreciated, thanks in advance.

               rc = Convert.ToInt16(textBox1.Text);
            if (rc == 3 || rc == 5 || rc == 7 || rc == 9 || rc == 11)
            {
                centro = rc / 2;
                centro1 = Math.Round(centro, 0);
                int[,] dim = new int[rc, rc];
                int v = 1, r = 0, c, x = 0;
                c = Convert.ToInt16(centro1);
                //rc2 = rc;
                for (x = 0; x < (rc*rc); x++)
                {
                    if (dim[r, c] >= 1)
                    {
                        r = r2 + 2;
                        c = c2 - 1;
                        dim[r, c] = v;
                    }
                    else
                    {
                        dim[r, c] = v;
                    }
                    c++;
                    r--;
                    v++;
                    if (r < 0)
                    {
                        r = rc -1;
                    };
                    if (c > (rc-1))
                    {
                        c = 0;
                    };
                    r2 = r;
                    c2 = c;                      
                } 
                else {
                textBox1.Text = "";
                MessageBox.Show("***Error***   blah blah blah");
            }'