C#

In the below code snippet, Ring() method defined in Classes "SmartPhone", "BasicPhone" etc is returning a custom datatype called "Sound". As far as I have read few topics, custom datatypes can be implemented using Classes, Structures etc.Normally, I have worked with methods returning in-built datatypes like int,string etc but have no idea about methods returning custom datatypes like "Sound" as per mentioned example. So, how should I write/define the Class "Sound" for the above program to work

If code execution calls "Phone.Ring()" statement in the foreach loop defined Main() method , let's say a message "MP3 music is playing" for Smartphone, "Polyphonic music is playing" for SemiSmartPhone, "8BitMusic is playing" for BasicPhone to be displayed on the console screen. 
Let me know if you need more details.To be honest, had posted in other forums, but couldn't get an answer yet.As far as I remember, this code example has been picked from codeproject.com I believe.  Thanks

class Sound
{
    ???// What should the implementation of this class be for the program    
       //to work
}
interface IRingable
{
    public Sound Ring();
}
class SmartPhone : IRingable
{
    public Sound Ring()
    {
        return PlayMp3Music();

    }

}
class SemiSmartPhone : IRingable
{
    public Sound Ring()
    {
        return PolyPhonicMusic();
    }
}
class BasicPhone : IRingable
{
    public Sound Ring()
    {
        return 8BitMusic();
    }
}

class Main
{
    public static void Main(string[] args)
    {
        List<IRingable> phones = new List<IRingable>();
        IRingable htc = new SmartPhone();
        phones.Add(htc);
        IRingable samsung = new SemiSmartPhone();
        phones.Add(samsung);
        IRingable nokia = new BasicPhone();
        phones.Add(nokia);
        // Lets Ring them all
        foreach (IRingable phone in phones)
        {
            phone.Ring();
        }
    }
}

public class MyWrapper : IDisposable
{
    private Session _mySession = new Session(); // This is the COM object

    public void Open() { _MySession.Open(); }
    public void Close() { _MySession.Close(); }

    public void Dispose() {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    public void Dispose(bool disposing) {
        _MySession.Close(); // Calling close without having called open is OK
    }
    ~MyWrapper() { Dispose(false); }    
}

//Username, Host and Password
string path = @"\\192.168.0.5\Share";
string userName = @"User";
string userPassword = "Password";
string userHost = "192.168.0.5";

//The Credentials
NetworkCredential theNetworkCredential = new NetworkCredential(userName, userPassword);
CredentialCache theNetCache = new CredentialCache();
theNetCache.Add(new Uri(path), "Basic", theNetworkCredential);

var g = theNetworkCredential.GetCredential(new Uri(path), "Basic");
var tt = CredentialCache.DefaultNetworkCredentials;

StorageFolder folder = await StorageFolder.GetFolderFromPathAsync(path);
IReadOnlyList<StorageFile> fileList = await folder.GetFilesAsync();
//Try to get all files
foreach (StorageFile sF in fileList)
{
    //do something with sF.DisplayName;
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace Workers {
    public partial class ManageUserRecords : Form {
        string getID { get; set; }
        string Emp_ID, Username, Password, Type, FirstName, MInitial, LastName, FullName, Address, Phone, Email;

        public ManageUserRecords() {
            InitializeComponent();
        }

        private void ManageUserRecords_Load(object sender, EventArgs e) {
            load_Dgv();
            hide_GridColumns();
            load_lb();
        }

        private void dataGridView1_CellClick(object sender, DataGridViewCellEventArgs e) {
            set_TxtBox();
        }

        private void dataGridView1_ColumnHeaderMouseClick(object sender, DataGridViewCellMouseEventArgs e) {
            set_TxtBox();
        }

        private void dataGridView1_KeyDown(object sender, KeyEventArgs e) {
            if (e.KeyCode == Keys.Up || e.KeyCode == Keys.Down) {
                set_TxtBox();
            }
        }

        private void btnInsert_Click(object sender, EventArgs e) {
            if ((string)btnInsert.Tag == "Add New") {
                btnInsert.Tag = "Save Add";
                btnInsert.Text = "Save";
                clear_All();
                txtFName.Select();
            } else if ((string)btnInsert.Tag == "Save Add") {
                if (txtFName.TextLength < 1 || txtLName.TextLength < 1) {
                    MessageBox.Show("First Name & Last Name is required");
                    return;
                } else if (txtUsername.TextLength < 1 || txtPassword.TextLength < 1) {
                    MessageBox.Show("Username & Password is required");
                    return;
                } else if (cbType.Text == "") {
                    MessageBox.Show("Account Type is required");
                    return;
                }

                btnInsert.Tag = "Add New";
                btnInsert.Text = "Add New";

                Username = txtUsername.Text;
                Password = txtPassword.Text;
                Type = cbType.Text;
                FirstName = txtFName.Text;
                MInitial = txtMInitial.Text;
                LastName = txtLName.Text;
                FullName = FirstName + " " + MInitial + " " + LastName;
                Address = txtAddress.Text;
                Phone = txtPhone.Text;
                Email = txtEmail.Text;

                new FormWorkers().insert_Record(FullName, Username, Password, Type, FirstName, MInitial, LastName, Address, Phone, Email);

                string userInfo = String.Format("Details:{0} Name : {1}{0} Address : {2}{0} Phone : {3}{0} Email : {4}{0}{0}Account:{0} Username : {5}{0} Type : {6}", Environment.NewLine, FullName, Address, Phone, Email, Username, Type);
                MessageBox.Show(String.Format("Record Added!{0}{0}" + userInfo, Environment.NewLine));

                load_Dgv();
                load_lb();

                clear_All();
            }
        }

        private void btnUpdate_Click(object sender, EventArgs e) {
            int count = dgvEmployees.SelectedRows.Count;
            if (count == 1) {
                if ((string)btnUpdate.Tag == "Update New") {
                    btnUpdate.Tag = "Save";
                    btnUpdate.Text = "Save";
                    accessControls();
                } else if ((string)btnUpdate.Tag == "Save") {
                    btnUpdate.Tag = "Update New";
                    btnUpdate.Text = "Update";

                    Emp_ID = getID;
                    Password = txtPassword.Text;
                    Type = cbType.Text;
                    FirstName = txtFName.Text;
                    MInitial = txtMInitial.Text;
                    LastName = txtLName.Text;
                    FullName = FirstName + " " + MInitial + " " + LastName;
                    Address = txtAddress.Text;
                    Phone = txtPhone.Text;
                    Email = txtEmail.Text;

                    new FormWorkers().update_Info(Emp_ID, FullName, Password, Type, FirstName, MInitial, LastName, Address, Phone, Email);

                    MessageBox.Show("Record updated");

                    load_Dgv();
                    load_lb();

                    clear_All();
                }
            } else {
                MessageBox.Show("Select an item from the list to update.");
            }
        }

        private void btnDelete_Click(object sender, EventArgs e) {
            int count = dgvEmployees.SelectedRows.Count;
            if (count == 1) {
                Emp_ID = getID;

                new FormWorkers().delete_Record(Emp_ID);

                MessageBox.Show("Record deleted");

                load_Dgv();
                load_lb();

                clear_All();
            } else {
                MessageBox.Show("Select an item from the list to delete.");
            }
        }

        void accessControls() {
            foreach (Control txt in this.Controls) {
                if (txt is TextBox) {
                    txt.Enabled = true;
                }
            }

            foreach (Control txt in groupBox1.Controls) {
                if (txt is TextBox) {
                    txt.Enabled = true;
                }
                cbType.Enabled = true;
            }
        }

        void load_Dgv() {
            new FormWorkers().load_Db();
            dgvEmployees.DataSource = FormWorkers.sqldt;
        }

        void load_lb() {
            listBox1.Items.Clear();
            new FormWorkers().load_List();
            foreach (DataRow dtrows in FormWorkers.lbdt.Rows) {
                FormWorkers.dtrow = dtrows;
                listBox1.Items.Add("(" + FormWorkers.dtrow["Emp_ID"] + ") " +
                    "Name: " + FormWorkers.dtrow["Name"]);
            }
        }

        void set_TxtBox() {
            DataGridViewRow CurrentRow = dgvEmployees.CurrentRow;
            getID = CurrentRow.Cells[0].Value.ToString();
            txtFName.Text = CurrentRow.Cells[5].Value.ToString();
            txtMInitial.Text = CurrentRow.Cells[6].Value.ToString();
            txtLName.Text = CurrentRow.Cells[7].Value.ToString();
            txtAddress.Text = CurrentRow.Cells[2].Value.ToString();
            txtPhone.Text = CurrentRow.Cells[3].Value.ToString();
            txtEmail.Text = CurrentRow.Cells[4].Value.ToString();
            txtUsername.Text = CurrentRow.Cells[8].Value.ToString();
            cbType.Text = CurrentRow.Cells[9].Value.ToString();
        }

        void hide_GridColumns() {
            int colcount = dgvEmployees.Columns.Count - 1;
            for (int i = 5; i <= colcount; i++) {
                dgvEmployees.Columns[i].Visible = false;
            }
        }

        void clear_All() {
            foreach (Control txt in this.Controls) {
                if (txt is TextBox || (string)btnDelete.Tag != "Delete") {
                    txt.Text = "";
                    if (txt.Enabled == true) {
                        txt.Enabled = false;
                    } else {
                        txt.Enabled = true;
                    }
                }
            }

            foreach (Control txt in groupBox1.Controls) {
                if (txt is TextBox || (string)btnDelete.Tag != "Delete") {
                    txt.Text = "";
                    if (txt.Enabled == true) {
                        txt.Enabled = false;
                        cbType.Enabled = false;
                    } else {
                        txt.Enabled = true;
                        cbType.Enabled = true;
                    }
                }
                cbType.SelectedIndex = 0;
            }
            dgvEmployees.ClearSelection();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Data.SqlClient;
using System.Windows.Forms;

namespace Workers {
    class FormWorkers {
        SqlCommand cmdSelect, sqlInsert, sqlUpdate, sqlDelete;
        SqlDataAdapter sqlSelect;
        SqlDataReader rdr;
        public static DataRow dtrow;
        public static DataTable lbdt;
        public static DataTable sqldt;

        public static string ID;

        private static FormWorkers _main = new FormWorkers();
        public static FormWorkers Main {
            get {
                return _main;
            }
        }

        public void load_List() {
            string connStr = @"Data Source=.\SQLEXPRESS_KEVIN;Database=Test;Integrated Security=true";
            using (SqlConnection conn = new SqlConnection(connStr)) {
                using (SqlDataAdapter sqlSelect = new SqlDataAdapter("SELECT Emp_ID,Name FROM Employees INNER JOIN Accounts ON Employees.Acct_ID=Accounts.Acct_ID WHERE Emp_ID >= 1", conn)) {
                    lbdt = new DataTable();
                    sqlSelect.Fill(lbdt);
                    dtrow = null;
                }
            }
        }

        public void load_Db() {
            try {
                string connStr = @"Data Source=.\SQLEXPRESS_KEVIN;Database=Test;Integrated Security=true";
                using (SqlConnection conn = new SqlConnection(connStr)) {
                    using (sqlSelect = new SqlDataAdapter("SELECT Emp_ID AS 'ID',Accounts.Name,Emp_Address AS 'Address',Emp_Contact AS 'Phone',Emp_Email AS 'Email',Emp_FName,Emp_MName,Emp_LName,Username,Type FROM Employees INNER JOIN Accounts ON Employees.Acct_ID=Accounts.Acct_ID", conn)) {
                        sqldt = new DataTable();
                        sqlSelect.Fill(sqldt);
                    }
                }
            } catch (SqlException err) {
                MessageBox.Show(err.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
        }

        public void insert_Record(string FullName, string Username, string Password, string Type, string FirstName, string MInitial, string LastName, string Address, string Phone, string Email) {
            try {
                string connStr = @"Data Source=.\SQLEXPRESS_KEVIN;Database=Test;Integrated Security=true";
                using (SqlConnection conn = new SqlConnection(connStr)) {
                    using (sqlInsert = new SqlCommand(
                        "INSERT INTO Accounts (Name,Username,Password,Type) VALUES (@name,@username,@password,@type);" +
                        "INSERT INTO Employees (Acct_ID,Emp_FName,Emp_MName,Emp_LName,Emp_Address,Emp_Contact,Emp_Email) " +
                        "SELECT TOP 1 Acct_ID,@FName,@MName,@LName,@Address,@Phone,@Email FROM Accounts ORDER BY Acct_ID DESC", conn)) {
                        sqlInsert.Parameters.AddWithValue("@name", FullName);
                        sqlInsert.Parameters.AddWithValue("@username", Username);
                        sqlInsert.Parameters.AddWithValue("@password", Password);
                        sqlInsert.Parameters.AddWithValue("@type", Type);
                        sqlInsert.Parameters.AddWithValue("@FName", FirstName);
                        sqlInsert.Parameters.AddWithValue("@MName", MInitial);
                        sqlInsert.Parameters.AddWithValue("@LName", LastName);
                        sqlInsert.Parameters.AddWithValue("@Address", Address);
                        sqlInsert.Parameters.AddWithValue("@Phone", Phone);
                        sqlInsert.Parameters.AddWithValue("@Email", Email);

                        conn.Open();
                        sqlInsert.ExecuteNonQuery();
                    }
                }
            } catch (SqlException err) {
                MessageBox.Show(err.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
        }

        public void update_Info(string Emp_ID, string FullName, string Password, string Type, string FirstName, string MInitial, string LastName, string Address, string Phone, string Email) {
            try {
                string connStr = @"Data Source=.\SQLEXPRESS_KEVIN;Database=Test;Integrated Security=true";
                using (SqlConnection conn = new SqlConnection(connStr)) {
                    conn.Open();
                    using (sqlUpdate = new SqlCommand(
                        "UPDATE Accounts SET Name=@name,Password=@password,Type=@type FROM Accounts INNER JOIN Employees ON Accounts.Acct_ID=Employees.Acct_ID WHERE Emp_ID=@Emp_ID;" +
                        "UPDATE Employees SET Emp_FName=@FName,Emp_MName=@MName,Emp_LName=@LName,Emp_Address=@Address,Emp_Contact=@Phone,Emp_Email=@Email WHERE Emp_ID=@Emp_ID", conn)) {
                        sqlUpdate.Parameters.AddWithValue("@name", FullName);
                        sqlUpdate.Parameters.AddWithValue("@password", Password);
                        sqlUpdate.Parameters.AddWithValue("@type", Type);
                        sqlUpdate.Parameters.AddWithValue("@FName", FirstName);
                        sqlUpdate.Parameters.AddWithValue("@MName", MInitial);
                        sqlUpdate.Parameters.AddWithValue("@LName", LastName);
                        sqlUpdate.Parameters.AddWithValue("@Address", Address);
                        sqlUpdate.Parameters.AddWithValue("@Phone", Phone);
                        sqlUpdate.Parameters.AddWithValue("@Email", Email);
                        sqlUpdate.Parameters.AddWithValue("@Emp_ID", Emp_ID);

                        sqlUpdate.ExecuteNonQuery();
                    }
                }
            } catch (SqlException err) {
                MessageBox.Show(err.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        public void delete_Record(string Emp_ID) {
            try {
                string connStr = @"Data Source=.\SQLEXPRESS_KEVIN;Database=Test;Integrated Security=true";
                using (SqlConnection conn = new SqlConnection(connStr)) {
                    using (sqlDelete = new SqlCommand(
                        "DELETE Accounts FROM Accounts INNER JOIN Employees ON Accounts.Acct_ID=Employees.Acct_ID WHERE Emp_ID=@ID;" +
                        "DELETE FROM Employees WHERE Emp_ID=@ID", conn)) {
                        sqlDelete.Parameters.AddWithValue("@ID", Emp_ID);

                        conn.Open();
                        sqlDelete.ExecuteNonQuery();
                    }
                }

            } catch (SqlException err) {
                MessageBox.Show(err.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }
    }
}