Public Class row
   Public data1 As Double
   Public data2 As Date
   Public data3 As Integer
   Public data4 As String
   Public data5 As Single
   Public data6 As Short
End Class

Public Class item
	Public ReadOnly Rows As New List(Of row)
	Public Sub New(rowCount As Integer)
		Rows = New List(Of row)(rowCount)
	End Sub
End Class

Public Class data
	Public ReadOnly Items As List(Of item)
   
	Public Sub New(itemCount As Integer)
		Items = New List(Of item)(itemCount)
	End Sub
End Class

Sub Main
	Const ItemCount As Integer = 3000000
	Const RowCount As Integer = 5
	
	Dim test As New data(ItemCount)
	For x As Integer = 0 To ItemCount
		Dim item As New item(RowCount)
		For r As Integer = 0 To RowCount
			item.Rows.Add(New row)
		Next
		test.Items.Add(item)
	Next
End Sub