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POWhat is "Best Practice" For Comparing Two Instances of a Reference Type?
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copied!<p>I came across this recently, up until now I have been happily overriding the equality operator (<strong>==</strong>) and/or <strong>Equals</strong> method in order to see if two references types actually contained the same <strong>data</strong> (i.e. two different instances that look the same).</p> <p>I have been using this even more since I have been getting more in to automated testing (comparing reference/expected data against that returned).</p> <p>While looking over some of the <a href="http://msdn.microsoft.com/en-us/library/ms229042(VS.80).aspx" rel="noreferrer">coding standards guidelines in MSDN</a> I came across an <a href="http://msdn.microsoft.com/en-us/library/7h9bszxx(VS.80).aspx" rel="noreferrer">article</a> that advises against it. Now I understand <em>why</em> the article is saying this (because they are not the same <em>instance</em>) but it does not answer the question:</p> <ol> <li><strong>What is the best way to compare two reference types?</strong></li> <li>Should we implement <a href="http://msdn.microsoft.com/en-us/library/system.icomparable.aspx" rel="noreferrer">IComparable</a>? (I have also seen mention that this should be reserved for value types only).</li> <li>Is there some interface I don't know about?</li> <li>Should we just roll our own?!</li> </ol> <p>Many Thanks ^_^</p> <h2>Update</h2> <p>Looks like I had mis-read some of the documentation (it's been a long day) and overriding <a href="http://msdn.microsoft.com/en-us/library/336aedhh(VS.71).aspx" rel="noreferrer">Equals</a> may be the way to go..</p> <blockquote> <p>If you are implementing reference types, you should consider overriding the Equals method on a reference type if your type looks like a base type such as a Point, String, BigNumber, and so on. Most reference types should not overload the <strong>equality</strong> operator, even <strong>if they override Equals</strong>. However, if you are implementing a reference type that is intended to have value semantics, such as a complex number type, you should override the equality operator.</p> </blockquote>

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