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    <p>The two pieces of code are <strong>not</strong> equivalent. The former ensures that all threads will always use the same lock object. The latter locks a lazily-initialized object, and there is absolutely nothing preventing multiple instantiations of your <code>_instance</code> dictionary, resulting in contents being lost.</p> <p>What is the purpose of the lock? Does the serve a purpose other than to guarantee single-initialization of the dictionary? Ignoring that it fails to accomplish this in the second example, if that is its sole intended purpose, then you may consider simply using the <code>Lazy&lt;T&gt;</code> class or a double-check locking pattern.</p> <p>But since this is a static member (and does not appear to capture outer generic parameters), it will presumably only be instantiated once per AppDomain. In that case, just mark it as <code>readonly</code> and initialize it in the declaration. You're probably not saving much this way.</p> <p>Since you are concerned with best practices: you should <em>never</em> use the <code>lock</code> construct on a mutable value; this goes for both static and instance fields, as well as locals. It is <em>especially</em> bad practice to lock on a <em>volatile</em> field, as the presence of that keyword indicates that you <em>expect</em> the underlying value to change. If you're going to lock on a field, it should almost always be a <code>readonly</code> field. It's also considered bad practice to lock on a method result; that applies to properties too, as properties are effectively a pair of specially-named accessor methods.</p>
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    1. POLocking a private static object
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    1. USMike Strobel
    1. USMike Strobel
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    1. COI recommend against the double-checked locking pattern. It is difficult to get right, and is only of benefit when there is high contention on the resource. The correct solution is not to go with a dangerous low-lock algorithm, it is to *eliminate the source of contention*.
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      1. USEric Lippert
    2. COAgreed. Double-check locking is best avoided unless you _really_ understand what you're doing (i.e., you understand the nuances of the memory model). Best to eliminate the problem altogether, i.e., get rid of the lazy initialization.
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      1. USMike Strobel
    3. COThanks! Please see OP edit that reflect your input. I hope this time I got it right.
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      1. USuser1615362
 

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