Question

Finding the last item in a collection

Asked by: dj__jebus

I have a collection call colCustomers with a key element CustomerID.  CustomerID is in the sequence 0001, 0002, 0003 etc... However sometimes a key may be skipped eg: 0001, 0002, 0004, 0005, 0006.  I need to be able to find out what the last CustomerID is so that I can create a new one that is one number higher.  I don't want to create in a missing spot and I don't want to resort the collection and change every CustomerID so non are skipped.

Thanks, Jebus

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Asked On
2003-11-07 at 20:21:52ID20791623
Topic

Visual Basic Programming

Participating Experts
2
Points
125
Comments
4

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Answers

 

by: SethiPosted on 2003-11-07 at 20:25:50ID: 9705768

Count the no. of items in the collection. The total count -1 would be the last item. example:

Collection.Item(Collection.Count-1)

 

by: dj__jebusPosted on 2003-11-07 at 20:31:29ID: 9705795

Well I have

NewCustomerID = colCustomers.Item(colCustomers.Count - 1).CustomerID + 1

and I get "This key is already asociated with an element of this collection" error.  I have tried this already and I think it does it because when a CustomerID is skipped the count is actually less than the highest CustomerID

Thanks, Jebus

 

by: Idle_MindPosted on 2003-11-07 at 21:37:25ID: 9706012

Why not just store the last used CustomerID externally in a variable and increment it?

 

by: Idle_MindPosted on 2003-11-07 at 21:45:18ID: 9706035

This is the major drawback of a collection...it takes a long time to find the last item since it has to walk the linked list item by item.  Also there is no way to do a reverse key lookup given an index.

An alternative scheme would be to store the last used customerID in the first spot in the collection!  The objects in a collection do not have to be of the same data type and it would not be hard to modify existing code to not use the first index.

20120131-EE-VQP-002

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