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Asked: 2026-05-12T00:44:41+00:00

I have generic list which must be a preserved order so I can retrieve

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I have generic list which must be a preserved order so I can retrieve the index of an object in the list. The problem is IndexOf is way too slow. If I comment the IndexOf out, the code runs fast as can be. Is there a better way, such as a preserved ordered hash list for c#?

Thanks,
Nate

  • Edit –
    The order in which the items are added/inserted is the order it needs to be. No sorting on them is necessary. Also this list has the potential to be updated often, add, remove, insert. Basically I need to translate the object to an index due to them being represented in a grid control so I can perform operations on the grid control based on index.
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  1. Editorial Team

    If it’s not sorted, but the order needs to be preserved, then you could have a separate Dictionary<YourClass, int> which would contain the index for each element.

    If you want a sorted list, then check previous posts – you can use SortedList<Tkey, TValue> in .Net 3.5, or sort it and use BinarySearch in older .Net versions.

    [Edit] You can find similar examples on the web, e.g.: OrderedList. This one internally uses an ArrayList and a HashTable, but you can easily make it generic.

    [Edit2] Ooops.. the example I gave you doesn’t implement IndexOf the way I described at the beginning… But you get the point – one list should be ordered, the other one used for quick lookup.

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