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    <p>All the answers here seem right: locks' usefulness is to block threads from acessing locked code concurrently. However, there are many subtleties in this field, one of which is that locked blocks of code are automatically marked as <strong>critical regions</strong> by the Common Language Runtime.</p> <p>The effect of code being marked as critical is that, if the entire region cannot be entirely executed, the runtime may consider that your entire Application Domain is potentially jeopardized and, therefore, unload it from memory. To quote <a href="http://msdn.microsoft.com/en-us/library/system.threading.thread.begincriticalregion.aspx" rel="noreferrer" title="Thread.BeginCriticalRegion Method (System.Threading)">MSDN</a>:</p> <blockquote> <p>For example, consider a task that attempts to allocate memory while holding a lock. If the memory allocation fails, aborting the current task is not sufficient to ensure stability of the AppDomain, because there can be other tasks in the domain waiting for the same lock. If the current task is terminated, other tasks could be deadlocked.</p> </blockquote> <p>Therefore, even though your application is single-threaded, this may be a hazard for you. Consider that one method in a locked block throws an exception that is eventually not handled within the block. Even if the exception is dealt as it bubbles up through the call stack, your critical region of code didn't finish normally. And who knows how the CLR will react?</p> <p>For more info, read <a href="http://tdanecker.blogspot.com/2007/08/do-never-ever-use-threadabort.html" rel="noreferrer" title="Thomas Danecker&#39;s Blog: Do never-ever use Thread.Abort!">this article on the perils of Thread.Abort()</a>.</p>
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    1. POlock keyword in C#
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    1. USAndré Chalella
    1. USAndré Chalella
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    1. COI don't believe you are right about the 'critical regions' marking for the CLR. This may be used by Monitor.Enter, but the user's protected code is not marked as such. See this article for an in depth understanding of critical regions: http://msdn.microsoft.com/en-us/magazine/cc163716.aspx
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      1. USMichael Donohue
    2. COI fail to see what would be wrong. Would you explain a bit clearer?
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      1. USAndré Chalella
    3. CO@Michael Donohue: I don't know about marking stuff as critical regions, but lock and Monitor.Enter are effectively the same. lock is just syntactic sugar for the `Enter-try-stuff-finally-Exit` pattern.
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      1. USR. Martinho Fernandes
 

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