Try this..
connection string is not properly set
SqlConnection myConnection = new SqlConnection("Data Source=GRIFFPC\SQLEXPRESS;Initial Catalog=Testing;Integrated Security=True");
myConnection.Open();
int sql = Convert.ToInt32("Delete from BQ_ShoppingCart where shoppingCartID = " + ShoppingCartID);
SqlCommand cmd = new SqlCommand(sql.ToString(),myConnection);
cmd.CommandType = CommandType.Text;
cmd.ExecuteNonQuery();
myConnection.Close();
no need to use cmd.Parameters