How to pass rows from List(of T) to a function

I am creating a List(of T) using a Reader.

After ensuring the List is sorted in a particular order I need to compare item values between rows and change an item value if required.

To do this I would like to pass two rows to a function for this comparison to take place. The Function is to be passed PreviousRow and NextRow and can return a Boolean or an integer. How do I pass the rows?

Whilst in the Function I will need to inspect item values from each row, how do I reference these items?

List is created from below code and sorted by the function further down:

			If reader3.HasRows Then

				Do While reader3.Read

					'Create a new instance of the CustomerInvoicedItems object to place this iteration value
					MyCustomerInvoicedItems = New CustomerInvoicedItems

					'Add the data to the CustomerInvoicedItems object's properties
					If String.IsNullOrEmpty(reader3("DespatchReceiptNumbers").ToString) Then
						MyCustomerInvoicedItems.DespatchReceiptNumbers = lngDespatchNumber
						MyCustomerInvoicedItems.DespatchReceiptNumbers = CInt(reader3("DespatchReceiptNumbers"))
						lngDespatchNumber = CInt(reader3("DespatchReceiptNumbers"))
					End If
					If Not IsDBNull(reader3("PrintSequenceNumber")) Then MyCustomerInvoicedItems.PrintSequenceNumber = CInt(reader3("PrintSequenceNumber"))
					If Not IsDBNull(reader3("FloydDocumentNumber")) Then MyCustomerInvoicedItems.FloydDocumentNumber = CInt(reader3("FloydDocumentNumber"))
					If Not IsDBNull(reader3("ItemCode")) Then MyCustomerInvoicedItems.ItemCode = reader3("ItemCode").ToString
					If Not IsDBNull(reader3("ItemDescription")) Then MyCustomerInvoicedItems.ItemDescription = reader3("ItemDescription").ToString
					If Not IsDBNull(reader3("LineQuantity")) Then
						MyCustomerInvoicedItems.LineQuantity = CInt(reader3("LineQuantity"))
						MyCustomerInvoicedItems.LineQuantity = 0
					End If
					If Not IsDBNull(reader3("UnitSellingPrice")) Then
						MyCustomerInvoicedItems.UnitSellingPrice = CDbl(reader3("UnitSellingPrice").ToString())
						MyCustomerInvoicedItems.UnitSellingPrice = 0
					End If
					If Not IsDBNull(reader3("UnitDiscountPercent")) Then
						MyCustomerInvoicedItems.UnitDiscountPercent = CDbl(reader3("UnitDiscountPercent").ToString())
						MyCustomerInvoicedItems.UnitDiscountPercent = 0
					End If
					If Not IsDBNull(reader3("LineTypeID")) Then MyCustomerInvoicedItems.LineTypeID = CInt(reader3("LineTypeID"))
					If Not IsDBNull(reader3("SOPInvoiceCreditLineID")) Then
						MyCustomerInvoicedItems.SOPInvoiceCreditLineID = CInt(reader3("SOPInvoiceCreditLineID"))
						MyCustomerInvoicedItems.SOPInvoiceCreditLineID = 0
					End If

					'Add the single object instance created above to the List (of InvoiceMainDetail) objects


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MyCustomerInvoicedItemsList = MyCustomerInvoicedItemsList.OrderBy(Function(x) x.SOPInvoiceCreditLineID).ToList()

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Who is Participating?
Paul_Harris_FusionConnect With a Mentor Commented:
If you only wanted to pass one item you could use:
For each item as CustomerInvoicedItems in MyCustomerInvoicedItemsList
     Call SomeFunction(item)

Since you want two items you need to have the index so:
for ix as integer =0 to  MyCustomerInvoicedItems.Count-2
     Debug.print  MyFunction (MyCustomerInvoicedItems(ix), MyCustomerInvoicedItems(ix+1) )

You could use IndexOf to find the index of a particular item that you already hold a reference to.

e.g.  ixCurrent = MyCustomerInvoicedItems.IndexOf(currentCustomerInvoicedItem)
Something like:

Public Function  MyFunction  (Byval previousRow as CustomerInvoicedItems,  Byval nextRow as CustomerInvoicedItems) as Boolean

     if previousRow.UnitDiscountPercent  <> nextRow.UnitDiscountPercent then
           ' do something
     end if

End Function

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and to call it :

Debug.print MyFunction (MyCustomerInvoicedItemsList.items(2),  MyCustomerInvoicedItemsList.items(3) )
TeDeSmAuthor Commented:
Thanks Paul, I see that the rows are referenced using the index MyFunction (MyCustomerInvoicedItemsList.items(2),  MyCustomerInvoicedItemsList.items(3) ) . 2 and 3 in your example, is there a way to get the index without counting through the list?
TeDeSmAuthor Commented:
Thanks Paul, spot on with your help.
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