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POWhat is a "mostly complete" (im)mutability approach for C#?
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  1. POWhat is a "mostly complete" (im)mutability approach for C#?
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    copied!<p>Since immutability is not fully baked into C# to the degree it is for F#, or fully into the framework (BCL) despite some support in the CLR, what's a fairly complete solution for (im)mutability for C#?</p> <p>My order of preference is a solution consisting of general patterns/principles compatible with</p> <ul> <li>a single open-source library with few dependencies</li> <li>a small number of complementary/compatible open-source libraries</li> <li>something commercial</li> </ul> <p>that</p> <ul> <li>covers Lippert's kinds of <a href="http://blogs.msdn.com/b/ericlippert/archive/2007/11/13/immutability-in-c-part-one-kinds-of-immutability.aspx" rel="nofollow noreferrer">immutability</a></li> <li>offers decent performance (that's vague I know)</li> <li>supports serialization</li> <li>supports cloning/copying (deep/shallow/partial?)</li> <li>feels natural in scenarios such as DDD, builder patterns, configuration, and threading</li> <li>provides immutable collections</li> </ul> <p>I'd also like to include patterns you as the community might come up with that don't exactly fit in a framework such as <a href="https://stackoverflow.com/questions/4310963/best-way-to-separate-read-and-write-concerns-using-interfaces/4311051#4311051">expressing mutability intent through interfaces</a> (where both clients that <em>shouldn't</em> change something and <em>may want to</em> change something can only do so through interfaces, and not the backing class (yes, I know this isn't true immutability, but sufficient):</p> <pre><code>public interface IX { int Y{ get; } ReadOnlyCollection&lt;string&gt; Z { get; } IMutableX Clone(); } public interface IMutableX: IX { new int Y{ get; set; } new ICollection&lt;string&gt; Z{ get; } // or IList&lt;string&gt; } // generally no one should get ahold of an X directly internal class X: IMutableX { public int Y{ get; set; } ICollection&lt;string&gt; IMutableX.Z { get { return z; } } public ReadOnlyCollection&lt;string&gt; Z { get { return new ReadOnlyCollection&lt;string&gt;(z); } } public IMutableX Clone() { var c = MemberwiseClone(); c.z = new List&lt;string&gt;(z); return c; } private IList&lt;string&gt; z = new List&lt;string&gt;(); } // ... public void ContriveExample(IX x) { if (x.Y != 3 || x.Z.Count &lt; 10) return; var c= x.Clone(); c.Y++; c.Z.Clear(); c.Z.Add("Bye, off to another thread"); // ... } </code></pre>
 

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