'Cargar el combobox1'
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Dim con As New MySqlConnection
        con.ConnectionString =  ("Server=localhost;DataBase=autos;uid=root;pwd=root").ToString
        con.Open()
        Dim query As String = "select distinct MARCA from autos"
        Dim cmd As New MySqlCommand(query, con)
        Dim reader As MySqlDataReader = cmd.ExecuteReader
        While reader.Read
            ComboBox1.Items.Add(reader.GetString("MARCA"))
        End While
 
        End Sub
'Cargar combobox2 dependiendo selección de combobox1'
Private Sub ComboBox1_SelectionChangeCommitted(sender As Object, e As EventArgs) Handles ComboBox1.SelectionChangeCommitted
        Dim con As New MySqlConnection
        con.ConnectionString = ("Server=localhost;DataBase=autos;uid=root;pwd=root").ToString
        con.Open()
        Dim query As String = "select MODELO from autos where MARCA='" + ComboBox1.SelectedItem + "'"
        Dim cmd As New MySqlCommand(query, con)
        Dim reader As MySqlDataReader = cmd.ExecuteReader
        While reader.Read
            ComboBox2.Items.Add(reader.GetString("MODELO"))
 
        End While
 
    End Sub