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copied!<p>Generally, if you must have the BEST indexed lookup performance it's best to build a List first and then turn it into a array thus paying a small penalty at first but avoiding any later. If the issue is that you will be continually adding new data and removing old data then you may want to use a ArrayList or List for convenience but keep in mind that they are just special case Arrays. When they "grow" they allocate a completely new array and copy everything into it which is extremely slow.</p> <p><a href="http://blogs.msdn.com/bclteam/articles/273454.aspx" rel="nofollow noreferrer">ArrayList</a> is just an Array which grows when needed. Add is amortized O(1), just be careful to make sure the resize won't happen at a bad time. Insert is O(n) all items to the right must be moved over. Remove is O(n) all items to the right must be moved over.</p> <p>Also important to keep in mind that List is not a linked list. It's just a typed ArrayList. The List <a href="http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx" rel="nofollow noreferrer">documentation</a> does note that it performs better in most cases but does not say why.</p> <p>The best thing to do is to pick a data structure which is appropriate to your problem. This depends one a LOT of things and so you may want to browse the <a href="http://msdn.microsoft.com/en-us/library/system.collections.generic.aspx" rel="nofollow noreferrer">System.Collections.Generic</a> Namespace. </p> <p>In this particular case I would say that if you can come up with a good key value <a href="http://msdn.microsoft.com/en-us/library/xfhwa508.aspx" rel="nofollow noreferrer">Dictionary</a> would be your best bet. It has insert and remove that approaches O(1). However, even with a Dictionary you have to be careful not to let it resize it's internal array (an O(n) operation). It's best to give them a lot of room by specifying a larger-then-you-expect-to-use initial capacity in the constructor. </p> <p>-Rick</p>

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