Comments on: Interesting (good) Behavior of Closures http://lostechies.com/chadmyers/2008/03/09/interesting-good-behavior-of-closures/ Software development, testing, and techie life Thu, 08 Mar 2012 22:19:00 +0000 hourly 1 http://wordpress.org/?v=3.4.2 By: Simone Busoli http://lostechies.com/chadmyers/2008/03/09/interesting-good-behavior-of-closures/#comment-155 Simone Busoli Fri, 14 Mar 2008 19:15:50 +0000 /blogs/chad_myers/archive/2008/03/08/interesting-good-behavior-of-closures.aspx#comment-155 Hi Chad, yeah, that's a cool behavior, and has somewhat become intuitive, since as lambda - or an anonymous method - are pointers to methods, not actually code which gets executed, therefore they create a closure around the variables of the environment and actually use them only when they are invoked. That's why, when you create loops which call anonymous methods, at times you need to declare an inner variable which disconnects from the outer closure and keeps the right value of the variable for each iterations, and the following example usually doesn't work as expected: var handle = new ManualResetEvent(false); for(int i = 0; i < 1000000; i++) ThreadPool.QueueUserWorkItem(() => { handle.WaitOne(); Console.WriteLine(i); }); handle.Set(); PS. Wrote it without the compiler, I'm not sure it does, but you get the idea. Hi Chad, yeah, that’s a cool behavior, and has somewhat become intuitive, since as lambda – or an anonymous method – are pointers to methods, not actually code which gets executed, therefore they create a closure around the variables of the environment and actually use them only when they are invoked.

That’s why, when you create loops which call anonymous methods, at times you need to declare an inner variable which disconnects from the outer closure and keeps the right value of the variable for each iterations, and the following example usually doesn’t work as expected:

var handle = new ManualResetEvent(false);

for(int i = 0; i < 1000000; i++)
ThreadPool.QueueUserWorkItem(() =>
{
handle.WaitOne();
Console.WriteLine(i);
});

handle.Set();

PS. Wrote it without the compiler, I’m not sure it does, but you get the idea.

]]> By: Jon Scolamiero http://lostechies.com/chadmyers/2008/03/09/interesting-good-behavior-of-closures/#comment-154 Jon Scolamiero Tue, 11 Mar 2008 17:33:52 +0000 /blogs/chad_myers/archive/2008/03/08/interesting-good-behavior-of-closures.aspx#comment-154 I like this behavior as it lets us do some setup early on in a method without worrying that the variable my not be instantiated yet. I like this behavior as it lets us do some setup early on in a method without worrying that the variable my not be instantiated yet.

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