SQL databashantering

Welcome to the menu
------------------------
1. Add vehicle
2. Move vehicle
3. Check out a vehicle
4. Search for a vehicle
5. Show an overview of the parkinglot
6. Exit program

//Sedan all kod för själva programmet i olika klasser osv

<connectionStrings>
    <add name ="connectToDataBase" connectionString="anslutningssträngen" providerName="System.Data.SqlClient"/>
  </connectionStrings>

string connString;
            connString = ConfigurationManager.ConnectionStrings["connectToDataBase"].ConnectionString; //connString som håller kopplingen från App.Config(?)
            SqlConnection sqlConnection = new SqlConnection(connString);
            sqlConnection.Open(); //Öppna anslutning före användning
            //Kod
            sqlConnection.Close(); //Stäng anslutning efter användning

Vehicle addedVehicle = new Vehicle();

            SqlCommand sqlCommand = new SqlCommand();
            SqlConnection sqlConnection = new SqlConnection(SQLDataSource.ConnectionString);
            sqlCommand.Connection = sqlConnection;
            sqlCommand.CommandText = "dbo.USP_AddVehicle";
            sqlCommand.CommandType = CommandType.StoredProcedure;

            addedVehicle.registrationNumber = UserInputs.GetVehicleRegistrationNumber();

            Console.Clear();

            addedVehicle.vehicleTypeID = UserInputs.GetVehicleType();

            Console.Clear();
            sqlCommand.Parameters.AddWithValue("@RegistrationNumber", addedVehicle.registrationNumber);
            sqlCommand.Parameters.AddWithValue("@VehicleType", addedVehicle.vehicleTypeID);

            var returnParameter = sqlCommand.Parameters.Add("@FirstParkingSpace", SqlDbType.Int);
            returnParameter.Direction = ParameterDirection.ReturnValue;

            int result = 0;

            try
            {
                using (sqlCommand.Connection)
                {
                    sqlCommand.Connection.Open();
                    int resultAddVehicle = sqlCommand.ExecuteNonQuery();


                    if (resultAddVehicle > 0)
                    {
                        Console.WriteLine("The vehicle has been sucessfully added");
                        result = (int)returnParameter.Value;
                    }
                    else
                    {
                        Console.WriteLine("The new vehicle has not been added due to an unforseen event");
                    }

                }
            }
            catch
            {
                Console.WriteLine("Something went wrong when trying to add a new vehicle. Please try again, if problem persists contact software suppport.");
                sqlCommand.Connection.Close();
            }

            return result;

Console.Clear();
            string connString;
            connString = ConfigurationManager.ConnectionStrings["connectToDataBase"].ConnectionString; 
            SqlConnection sqlConnection = new SqlConnection(connString);
            sqlConnection.Open();
            string firstName, lastName, gender;
            int birth;
            Console.Write("Enter your firstname: ");
            firstName = Console.ReadLine();
            Console.Clear();
            Console.Write("Enter your lastname: ");
            lastName = Console.ReadLine();
            Console.Clear();
            Console.Write("Enter your gender: ");
            gender = Console.ReadLine();
            Console.Clear();
            Console.Write("Enter your birth: ");
            birth = int.Parse(Console.ReadLine());

            SqlCommand cmd = new SqlCommand("INSERT INTO Person VALUES('" + firstName + "', '" + lastName + "', '" + gender + "', '" + birth + "')", sqlConnection);
            int i = cmd.ExecuteNonQuery();
            if (i > 0)
            {
                Console.Clear();
                Console.WriteLine("Insertion successfull!\n\n");
                Console.Write("Press any key to return to the menu. . .");
                Console.ReadKey();
            }
            else
            {
                Console.Clear();
                Console.WriteLine("Someting went wrong!\n\n");
                Console.Write("Press any key to return to the menu. . .");
                Console.ReadKey();
            }
            sqlConnection.Close();

CREATE PROCEDURE [spAddPerson]
@FirstName nvarchar(30),
@LastName nvarchar(30),
@Gender nvarchar(6),
@Birth date,
@person_id int OUT
AS
BEGIN
INSERT INTO [dbo].[Person]
VALUES (@FirstName, @LastName, @Gender, @Birth)
SELECT @person_id = SCOPE_IDENTITY()
END

Console.Clear();
            Person addPerson = new Person();
            string connString = ConfigurationManager.ConnectionStrings["connectToDataBase"].ConnectionString;
            using (SqlConnection connection = new SqlConnection(connString))
            {
                SqlCommand cmd = new SqlCommand("spAddPerson", connection);
                cmd.CommandType = System.Data.CommandType.StoredProcedure;

                addPerson.FirstName = UserInputHandler.FirstName();
                addPerson.LastName = UserInputHandler.LastName();
                addPerson.Gender = UserInputHandler.Gender();
                addPerson.Birth = UserInputHandler.Birth();

                cmd.Parameters.AddWithValue("[@Firstname]", addPerson.FirstName);
                cmd.Parameters.AddWithValue("[@LastName]", addPerson.LastName);
                cmd.Parameters.AddWithValue("[@Gender]", addPerson.Gender);
                cmd.Parameters.AddWithValue("[@Birth]", addPerson.Birth);

                SqlParameter outputParam = new SqlParameter();
                outputParam.ParameterName = "@person_id";
                outputParam.SqlDbType = System.Data.SqlDbType.Int;
                outputParam.Direction = System.Data.ParameterDirection.Output;
                cmd.Parameters.Add(outputParam);

                try
                {
                    connection.Open();
                    int i = cmd.ExecuteNonQuery();
                    if(i > 0)
                    {
                        Console.Clear();
                        Console.Write("Person successfully added!");
                        Console.ReadKey();
                    }
                    else
                    {
                        Console.Clear();
                        Console.Write("Something went wrong!");
                        Console.ReadKey();
                    }
                }
                catch(Exception msg)
                {
                    Console.Clear();
                    Console.WriteLine(msg);
                    Console.ReadKey();
                }
                finally
                {
                    connection.Close();
                }