Private Sub cmbCity_Enter(ByVal sender As Object, ByVal e As System.EventArgs) _
  Handles cmbCity.Enter
 
        Dim arrSubFolders As New ArrayList
        arrSubFolders.Add("A")
        arrSubFolders.Add("B")
        arrSubFolders.Add("C")
 
        With cmbCity
            .DataSource = arrSubFolders
            .AutoCompleteSource = AutoCompleteSource.ListItems
            .AutoCompleteMode = AutoCompleteMode.Append
        End With
 
    End Sub