Index and length must refer to a location within the string.

Question

private bool isvalidyearcode(string ycode)
       {
           if (Convert.ToInt32(ycode.Substring(1, 4).ToString()) == 0 | Convert.ToInt32(ycode.Substring(3, 2).ToString()) + 1 != Convert.ToInt32(ycode.Substring(6, 7).ToString()) | Convert.ToInt32(ycode.Substring(5, 1)).ToString() != "-")  //error
           {
               MessageBox.Show("Invalid Year code");
               return false;
           }
           return true;
       }