مبتدی: درخواست کمک برای تقویم فارسی در VB

An unhandled exception of type 'System.NullReferenceException' occurred in level2_memo project.exe

Additional information: Object reference not set to an instance of an object.

'---------------------------------------------- کد مربوطه---------

Public Sub persian_cal()
Dim g As Globalization.PersianCalendar
Me.Label6.Text = g.GetYear(Now)
Me.Label8.Text = g.GetDayOfWeek(Now).ToString
Dim i As Integer
Dim a As String
i = g.GetMonth(Now)
Select Case i
Case 1
a = "فروردین"
Case 2
a = "اردیبهشت"
Case 3
a = "خرداد"
Case 4
a = "تیر"
Case 5
a = "مرداد"
Case 6
a = "شهریور"
Case 7
a = "مهر"
Case 8
a = "آبان"
Case 9
a = "آذر"
Case 10
a = "دی"
Case 11
a = "بهمن"
Case 12
a = "اسفند"
Case Else
a = "نامشخص"

End Select
Me.Label7.Text = a
End Sub