How to retrieve a data from a table and insert into another table?

See more:

C#

ASP.NET

SQL

I am trying to retrieve "customer_id" from Customer table and insert it into

fare_tariff(tariff_id, customer_id, total_price)

So I retrieve the customer_id from Customer table as below:

using (SqlCommand command = new SqlCommand("SELECT customer_id FROM Customer WHERE UserName = '" + username + "' Password = '"+password +"' ", connection))
                {
                    string cust_id = customer_id.ToString();
                    SqlDataReader myReader = command.ExecuteReader();

                     if (myReader.Read())
                        {
                            cust_id = myReader["customer_id"].ToString();
                        }

                    int c_id = Convert.ToInt32(cust_id);

                   myReader.Close();
                   custID(c_id);
                }

and insert the customer_id into table fare_tariff like below:

using (SqlCommand command = new SqlCommand("INSERT INTO flight_reservation(tariff_id, customer_id, total_price) VALUES(@val1,@val2,@val3)", connection))
                {

                    command.Parameters.Add("@val1", SqlDbType.Int).Value = tariff_id;
                    command.Parameters.Add("@val2", SqlDbType.Int).Value = customer_id;
                    command.Parameters.Add("@val3", SqlDbType.VarChar).Value = total_price.ToString();

                    command.ExecuteNonQuery();
                }

I declared customer_id as a variable for storing customer_id.

Problem is: tariff_id and total_price inserted successfully but the column customer_id is null yet.

Help needed.