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POc# vb: Should we use System.Lazy for resource-intensive task? (when threading is not needed)
 

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  1. POc# vb: Should we use System.Lazy for resource-intensive task? (when threading is not needed)
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    <p>I'm wondering is there some kind of JIT-hack going on with System.Lazy to make things more performant or is it purely a "normal class"?</p> <p>From the page <a href="http://msdn.microsoft.com/en-us/library/dd642331.aspx" rel="nofollow">http://msdn.microsoft.com/en-us/library/dd642331.aspx</a> it says:</p> <blockquote> <p>Use an instance of Lazy(Of T) to defer the creation of a large or resource-intensive object or the execution of a resource-intensive task, particularly when such creation or execution might not occur during the lifetime of the program.</p> </blockquote> <p>but i can defer the execution of a resource-intensive task using a simple boolean flag couldn't i? So what exactly is the difference? (other than System.Lazy has additional overheads for no apparent "syntax sugar" gains)</p> <p>With a simple boolean flag its simply:</p> <pre><code>if (!deferred) { //run resource-intensive task } </code></pre> <p>Edit: </p> <p>here's an example</p> <pre><code>class Human{ System.Lazy&lt;String&gt; name = new System.Lazy&lt;String&gt;(() =&gt; { //code here takes 4 seconds to run return "the value"; }); String Name { get { return name.Value; } } } </code></pre> <p>vs</p> <pre><code>class Human { String name; bool name_initiated; String Name { get { if (!name_initiated) { //code here takes 4 seconds to run name = "the value"; name_initiated = true; } return name; } } } </code></pre> <p>6 May: now i use this alot. And i really mean alot alot. i use it whenever i need to cache data (even when the computation is 0.1 second or lesser). Hence my question, should i be worried? Now i know you will tell me to profile the app, but im building the library first before i build the app and by that time if the app has problems that would mean Major change </p>
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    1. COCan you show techique how to defer loading/execution with simple boolean flag? You can start with http://en.wikipedia.org/wiki/Call_by_need
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      1. POc# vb: Should we use System.Lazy for resource-intensive task? (when threading is not needed)
      1. USNick Martyshchenko
    2. COI'll let someone less lazy formulate an answer... Oh by the way F# uses `Lazy<T>` and provides a bit of syntax sugar. `let ls = lazy([1;2;3])`
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    3. CO@Nick i've edited the question to show how to defer loading/execution with a simple boolean flag.
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