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POHow to write copy-on-write list in .NET
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  1. POHow to write copy-on-write list in .NET
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    copied!<p>How to write a thread-safe list using copy-on-write model in .NET?</p> <p>Below is my current implementation, but after lots of reading about threading, memory barriers, etc, I know that I need to be cautious when multi-threading without locks is involved. Could someone comment if this is the correct implementation?</p> <pre><code>class CopyOnWriteList { private List&lt;string&gt; list = new List&lt;string&gt;(); private object listLock = new object(); public void Add(string item) { lock (listLock) { list = new List&lt;string&gt;(list) { item }; } } public void Remove(string item) { lock (listLock) { var tmpList = new List&lt;string&gt;(list); tmpList.Remove(item); list = tmpList; } } public bool Contains(string item) { return list.Contains(item); } public string Get(int index) { return list[index]; } } </code></pre> <p><strong>EDIT</strong></p> <p>To be more specific: is above code thread safe, or should I add something more? Also, will all thread eventually see change in <code>list</code> reference? Or maybe I should add <code>volatile</code> keyword on list field or Thread.MemoryBarrier in Contains method between accessing reference and calling method on it?</p> <p>Here is for example <a href="http://developer.classpath.org/doc/java/util/concurrent/CopyOnWriteArrayList-source.html" rel="nofollow noreferrer">Java implementation</a>, looks like my above code, but is such approach also thread-safe in .NET?</p> <p>And <a href="https://stackoverflow.com/questions/11963972/in-java-can-i-depend-on-reference-assignment-being-atomic-to-implement-copy-on-w?rq=1">here</a> is the same question, but also in Java.</p> <p><a href="https://stackoverflow.com/questions/14921043/what-has-changed-in-the-memory-model-in-net-4-5">Here</a> is another question related to this one.</p>
 

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