Executing Stored Procedure using Command Object

The Stored Procedure was verified that has no problem by SSMS.

I made client code that call Stored Procedure like following.

    class CustomerOrder
    {
        string _connString = "Data Source=MyPC\\SQLTEST;Initial Catalog=TSQL2012;User ID=sa;Password=1234567";
        public List<string> GetCustomerOrderList(int custid)
        {
            List<string> orderList = new List<string>();
            using (SqlConnection customerOrderConnection = new SqlConnection(_connString))
            {
                using (SqlCommand customerOrderCommand = new SqlCommand())
                {
                    try
                    {
                        customerOrderConnection.Open();
                        customerOrderCommand.Connection = customerOrderConnection;
                        customerOrderCommand.CommandText = "GetCustomerOrders";

                        SqlParameter custidParameter = new SqlParameter();
                        custidParameter.ParameterName = "@custid";
                        custidParameter.Direction = ParameterDirection.Input;
                        custidParameter.SqlDbType = SqlDbType.Int;
                        custidParameter.Value = custid;
                        customerOrderCommand.Parameters.Add(custidParameter);

                        SqlParameter fromdateParameter = new SqlParameter();
                        fromdateParameter.ParameterName = "@fromdate";
                        fromdateParameter.Direction = ParameterDirection.Input;
                        fromdateParameter.SqlDbType = SqlDbType.DateTime;
                        DateTime dt1 = new DateTime(2007, 01, 01);
                        fromdateParameter.Value = dt1;
                        customerOrderCommand.Parameters.Add(fromdateParameter);

                        SqlParameter todateParameter = new SqlParameter();
                        todateParameter.ParameterName = "@todate";
                        todateParameter.Direction = ParameterDirection.Input;
                        todateParameter.SqlDbType = SqlDbType.DateTime;
                        DateTime dt2 = new DateTime(2008, 01, 01);
                        todateParameter.Value = dt2;
                        customerOrderCommand.Parameters.Add(todateParameter);

                        SqlParameter outputParameter = customerOrderCommand.Parameters.Add("@numrows", SqlDbType.Int);
                        outputParameter.Direction = ParameterDirection.Output;
                        customerOrderCommand.CommandType = CommandType.StoredProcedure;
                        using (SqlDataReader customerOrderDataReader = customerOrderCommand.ExecuteReader())
                        {
                            while (customerOrderDataReader.Read())
                            {
                                orderList.Add(customerOrderDataReader.GetString(0));
                            }
                        }
                        return orderList;
                    }
                    catch (SqlException ex)
                    {
                        throw ex;
                    }
                }
            }
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            CustomerOrder co = new CustomerOrder();
            foreach (string order in co.GetCustomerOrderList(1))
            {
                Console.WriteLine("{0}", order);
            }
        }
    }

If run, following error occurs.

Could not find Stored Procedure "GetCustomerOrders"....

Can you help me to fix this code?