C#

public void Download(string user,string filename, out byte[] file)
        {
            file = new byte[1];

            if (!System.IO.Directory.Exists("Share"))
                System.IO.Directory.CreateDirectory("Share");

            foreach (string the in System.IO.Directory.GetFiles("Share")) 
            {
                if(the.Contains(filename))
                if (System.IO.File.Exists(the))
                {
                    file = System.IO.File.ReadAllBytes(the);
                    AddLog(string.Format("> File: {0} has been downloaded at {1}. by {2}",(new System.IO.FileInfo(the)).Name,DateTime.Now.ToShortTimeString(),user));
                    break;
                }
            }

            if (file.Length == 1)
                file = null;
        }

[ImportingConstructor]
public MainForm([ImportMany] IEnumerable<AudioPlugin> content)
{
    InitializeComponent();
    listBox.DisplayMember = "Name";
    foreach (var listing in content)
    {
        listBox.Items.Add(listing);
    }
}

[Export(typeof(INAudioPlugin))]
    public class RecordingPanelPlugin : AudioPlugin
    {
        private string _customer { get; set; }

        public void ConnectionString()
        {
            using (var conn = new SqlCeConnection("Data Source=MyDatabase.sdf;Password=pass;Persist Security Info=True"))
            {
                conn.Open();
                var comm = new SqlCeCommand("SELECT * FROM main", conn);
                SqlCeDataReader reader = comm.ExecuteReader();

                while (reader.Read())
                {
                    _customer += (string)(reader["CustomerName"]);
                }
            }
        }


        public string Name
        {
            get
            {
                ConnectionString();
                return _customer;
            }
        }

        public Control CreatePanel()
        {
            return new RecordingPanel();
        }
    }

var plugin = (INAudioPlugin)listbox.SelectedItem;

[ImportingConstructor]
public MainForm([ImportMany] IEnumerable<INAudioPlugin> content)
{
    InitializeComponent();

    using (var conn = new SqlCeConnection("Data Source=MyDatabase.sdf;Password=pass;Persist Security Info=True"))
    {
        conn.Open();
        var comm = new SqlCeCommand("SELECT * FROM main", conn);
        SqlCeDataReader reader = comm.ExecuteReader();

        while (reader.Read())
        {
            _customer = (string)(reader["CustomerName"]);
    listbox.Items.Add(_customer);
        }
    }
}

private INAudioPlugin currentPlugin;

private void listbox_SelectedIndexChanged(object sender, EventArgs e)
{
    var plugin = (INAudioPlugin)listbox.SelectedItem;
    if (plugin != currentPlugin)
    {
        this.currentPlugin = plugin;
        DisposeCurrentListing();
        var control = plugin.CreatePanel();
        control.Dock = DockStyle.Fill;
        contentPanel.Controls.Add(control);
    }
}