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POCan a base-class method return this, even in a derived class?
 

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    <p>I'd like to be able to have a method in a C# base class, callable on objects of several derived classes, that returns the object itself, and have the CLR know what type the object really is - <em>i.e.</em>, the appropriate derived type. <strong>Can someone suggest a way to do it?</strong> Other, of course, than return type covariance, which C# doesn't have.</p> <p>Something like this, except that <code>Method()</code>'s return type should be the type of the derived class, not the base:</p> <pre><code>public abstract class Base { public Base Method() { return this; } } public class Derived1: Base { ... } public class Derived2: Base { ... } public class Main { public static int Main() { Derived1 d1 = new Derived1(); Derived1 x = d1.Method(); Derived2 d2 = new Derived2(); Derived2 y = d2.Method(); } } </code></pre> <p>I can only think of two ways to make this work, and I don't like either of them:</p> <ol> <li><p>Cast the result of Method() to the expected type (<em>e.g.</em>, <code>Derived1 x = (Derived) d1.Method();</code>). But casts are the tool of the Devil, and besides, the intent of the method is to return a <code>Derived1</code> or <code>Derived2</code> or ..., not a <code>Base</code>.</p></li> <li><p>Declare <code>Method()</code> as abstract in the base and implement it separately in each derived class. But that runs exactly counter to the idea of factoring out common methods. The <code>Method()</code> would be identical in each case except for its return type.</p></li> </ol>
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    1. USRoss Patterson
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    1. CO+1 for 'tools of the Devil'
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