vb.net显示最早的日期

Question

Book Collection作为介绍类的编码项目，需要显示最早的打印年份。它最初是显示的，但不会写入文件，因为我正在尝试将字符串转换为整数。正在使用的代码：

Private Sub findOldest()
    Dim oldest As Integer = 4000
    Dim printDate As Integer
    For index As Integer = 2 To count * 4 - 1 Step 4
        printDate = CInt(bookData(index))
        If oldest > printDate Then
            oldest = printDate
        End If
    Next
    lblOldestBook.Text = CStr(oldest)
End Sub