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POC# Performance setting value for each list item
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  1. POC# Performance setting value for each list item
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    copied!<p>I am trying to find the fasted way to set a specific property of every item in a generic list.</p> <p>Basicly the requirement is to iterate over a list of items and resetting the IsHit property to FALSE. Only the items in a second "hit"-list should be set to TRUE afterwards.</p> <p>My first attempt looked like this:</p> <pre><code>listItems.ForEach(delegate(Item i) { i.IsHit = false; }); foreach (int hitIndex in hits) { listItems[hitIndex - 1].IsHit = true; } </code></pre> <p>Note: hits is 1-based, the items list is 0-based.</p> <p>Then i tried to improve the speed and came up with this:</p> <pre><code>for (int i = 0; i &lt; listItems.Count; i++) { bool hit = false; for (int j = 0; j &lt; hits.Count; j++) { if (i == hits[j] - 1) { hit = true; hits.RemoveAt(j); break; } } if (hit) { this.listItems[i].IsHit = true; } else { this.listItems[i].IsHit = false; } } </code></pre> <p>I know this is a micro optimization but it is really time sensitive code, so it would make sense to improve this code beyond readibility... and just for fun of course ;-)</p> <p>Unfortuanetly I don't really see any way to improve the code further. But I probably missed something.</p> <p><br><br> Thanks</p> <p>PS: Code in C# / .NET 2.0 would be preferred.</p> <hr> <p>I ended up switching to Eamon Nerbonne solution. But then I noticed something weird in my benchmarks.</p> <p>The delegate:</p> <pre><code>listItems.ForEach(delegate(Item i) { i.IsHit = false; }); </code></pre> <p>is faster than:</p> <pre><code>foreach (Item i in listItems) { i.IsHit = false; } </code></pre> <p>How is that possible?</p> <p>I tried to look at IL but thats just way over my head... I only see that the delegates results in fewer lines, whatever that means.</p>
 

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