Post a purchase order in VB.NET

Posting a purchase order in VB.NET is similar to posting an invoice, you're using Pop-prefixed classes rather than Invoice-Prefix classes, and using a different underlying schema, but otherwise, it's more or less the same, here is a code example:
Private Sub btnPurchaseOrderPost_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPurchaseOrderPost.Click
Dim PurchaseOrderRecord As SageDataObject50.PopRecord = ws50.CreateObject("PopRecord")
Dim PurchaseOrderPost As SageDataObject50.PopPost = ws50.CreateObject("PopPost")

'Set the type of invoice so we can find the next available number
'PurchaseOrderPost.Type = SageDataObject50.LedgerType.sdoLedgerService

'Loop for Number of Items on the Invoice
Dim PurchaseOrderItem As SageDataObject50.PopItem = PurchaseOrderPost.Items.Add()

' This is the text for the line

PurchaseOrderItem.Fields.Item("Text").Value = "Invoice Line Text"
PurchaseOrderItem.Fields.Item("Service_Item_Lines").Value = CLng(1)
PurchaseOrderItem.Fields.Item("Net_Amount").Value = CLng(100)
PurchaseOrderItem.Fields.Item("Full_Net_Amount").Value = CLng(100)
PurchaseOrderItem.Fields.Item("Tax_Amount").Value = CLng(0)
PurchaseOrderItem.Fields.Item("Nominal_Code").Value = "4000" 'Sales
PurchaseOrderItem.Fields.Item("Tax_Code").Value = "T9"
PurchaseOrderItem.Fields.Item("Tax_Rate").Value = CDec(0)

'Populate Header Information
' see http://www.sagedataobjects.com/line50v9schema.asp
' PURCHASE_ORDER for schema
PurchaseOrderPost.Header("Order_Date").value = DateTime.Now.ToString("MM/dd/yyyy")
PurchaseOrderPost.Header("Notes_1").value = "Notes 1"
PurchaseOrderPost.Header("Notes_2").value = ""
PurchaseOrderPost.Header("Notes_3").value = ""
PurchaseOrderPost.Header("Taken_By").value = ""
PurchaseOrderPost.Header("Order_Number").value = ""
PurchaseOrderPost.Header("Payment_Ref").value = ""
PurchaseOrderPost.Header("Global_Nom_Code").value = ""
PurchaseOrderPost.Header("Global_Details").value = ""
PurchaseOrderPost.Header("Items_Net").value = CDec(100)
PurchaseOrderPost.Header("Items_Tax").value = CDec(0)

'Read the first customer
PurchaseOrderRecord.MoveFirst()
PurchaseOrderPost.Header("Account_Ref").value = CStr(PurchaseOrderRecord.Fields.Item("Account_Ref").Value)
PurchaseOrderPost.Header("Name").value = CStr(PurchaseOrderRecord.Fields.Item("Name").Value)
PurchaseOrderPost.Header("Address_1").value = CStr(PurchaseOrderRecord.Fields.Item("Address_1").Value)
PurchaseOrderPost.Header("Address_2").value = CStr(PurchaseOrderRecord.Fields.Item("Address_2").Value)
PurchaseOrderPost.Header("Address_3").value = CStr(PurchaseOrderRecord.Fields.Item("Address_3").Value)
PurchaseOrderPost.Header("Address_4").value = CStr(PurchaseOrderRecord.Fields.Item("Address_4").Value)
PurchaseOrderPost.Header("Address_5").value = CStr(PurchaseOrderRecord.Fields.Item("Address_5").Value)
PurchaseOrderPost.Header("Del_Address_1").value = CStr(PurchaseOrderRecord.Fields.Item("Del_Address_1").Value)
PurchaseOrderPost.Header("Del_Address_2").value = CStr(PurchaseOrderRecord.Fields.Item("Del_Address_2").Value)
PurchaseOrderPost.Header("Del_Address_3").value = CStr(PurchaseOrderRecord.Fields.Item("Del_Address_3").Value)
PurchaseOrderPost.Header("Del_Address_4").value = CStr(PurchaseOrderRecord.Fields.Item("Del_Address_4").Value)
PurchaseOrderPost.Header("Del_Address_5").value = CStr(PurchaseOrderRecord.Fields.Item("Del_Address_5").Value)
PurchaseOrderPost.Header("Contact_Name").value = CStr(PurchaseOrderRecord.Fields.Item("Contact_Name").Value)


PurchaseOrderPost.Header("Order_Number").value = CLng(101)


If PurchaseOrderPost.Update Then
MessageBox.Show("Purchase Order Created Successfully")
Else
MessageBox.Show("Purchase Order NOT Created")
End If

End Sub