problemer med kald af metode c#

CSharp kode 

 using System;   
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 using MySql.Data.MySqlClient;
 using System.Windows.Forms;
 
 namespace physio
 {
     class mySql
     {
         private MySqlConnection connection;
         private string server;
         private string database;
         private string uid;
         private string password;
         public string Name { get; set; }
         public string Address1 { get; set; }
         public string Attn { get; set; }
 
         public mySql()
         {
             Initialize();
         }
         //Initialize values
         private void Initialize()
         {
             server = "XXXXX";
             database = "XXXXX";
             uid = "XXXXX";
             password = "XXXXX";
             string connectionString;
             connectionString = "SERVER=" + server + ";" + "DATABASE=" +
             database + ";" + "UID=" + uid + ";" + "PASSWORD=" + password + ";";
 
             connection = new MySqlConnection(connectionString);
         }
 
         //open connection to database
         private bool OpenConnection()
         {
             try
             {
                 connection.Open();
                 return true;
             }
             catch (MySqlException ex)
             {
                 //When handling errors, you can your application's response based 
                 //on the error number.
                 //The two most common error numbers when connecting are as follows:
                 //0: Cannot connect to server.
                 //1045: Invalid user name and/or password.
                 switch (ex.Number)
                 {
                     case 0:
                    MessageBox.Show("Cannot connect to server.  Contact administrator");
                         break;
 
                     case 1045:
                         MessageBox.Show("Invalid username/password, please try again");
                         break;
                         
                 }
                 return false;
             }
         }
 
         //Close connection
         private bool CloseConnection()
         {
             try
             {
                 connection.Close();
                 return true;
             }
             catch (MySqlException ex)
             {
                 MessageBox.Show(ex.Message);
                 return false;
             }
         }
 
         
         
        public List<object> LoadCustomers()
         {
             var listOfCustomers = new List<object>();
             string query = "SELECT * FROM customers where id = '1200'";
 
             //Open connection
             this.OpenConnection();
             {
                 //Create Command
                 MySqlCommand cmd = new MySqlCommand(query, connection);
                 //Create a data reader and Execute the command
                 MySqlDataReader dataReader = cmd.ExecuteReader();
 
                 //Read the data and store them in the list
                 while (dataReader.Read())
                 {
                     mySql c = new mySql();
                     c.Name = dataReader["Name"].ToString();
                     c.Address1 = dataReader["Address1"].ToString();
                     c.Attn = dataReader["Attn"].ToString();
                     listOfCustomers.Add(c);
                 }
 
                 //close Data Reader
                 dataReader.Close();
 
                 //close Connection
                 this.CloseConnection();
 
                 //return list to be displayed
                 return listOfCustomers;
 
             }
             
         }
     } 
 }

CSharp kode 

 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Data;
 using System.Drawing;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 using System.Windows.Forms;
 
 namespace physio
 {
     public partial class Managed : Form
     {
         mySql managed = new mySql();
         public Managed()
         {
             InitializeComponent();
             
 
 
 
             List<object> customers = new List<object>();
           customers.Add(managed.LoadCustomers());
 
             listBox1.DataSource = customers;
 
         }
     }
 }