Per essere più preciso:

codice:
Imports MySql.Data.MySqlClient

Public Class Form1
 
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim Connection As New MySqlConnection("Server=localhost; Database=appdata; Uid=root; Pwd=root;")
Dim Adapter As New MySqlDataAdapter()
 
Try
Connection.Open()
Adapter.SelectCommand = New MySqlCommand("SELECT * FROM Customers;", Connection)
Adapter.Fill(MainDatabase.Customers)
Dall'ultima linea cominciano i problemi col MainDatabase.
Codice completo