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POHow do I dispatch to a method based on a parameter's runtime type in C# < 4?
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copied!<p>I have an object <code>o</code> which guaranteed at runtime to be one of three types <code>A</code>, <code>B</code>, or <code>C</code>, all of which implement a common interface <code>I</code>. I can control <code>I</code>, but not <code>A</code>, <code>B</code>, or <code>C</code>. (Thus I could use an empty marker interface, or somehow take advantage of the similarities in the types by using the interface, but I can't add new methods or change existing ones in the types.)</p> <p>I also have a series of methods <code>MethodA</code>, <code>MethodB</code>, and <code>MethodC</code>. The runtime type of <code>o</code> is looked up and is then used as a parameter to these methods.</p> <pre><code>public void MethodA(A a) { ... } public void MethodB(B b) { ... } public void MethodC(C c) { ... } </code></pre> <p>Using this strategy, right now a check has to be performed on the type of <code>o</code> to determine which method should be invoked. Instead, I would like to simply have three overloaded methods:</p> <pre><code>public void Method(A a) { ... } // these are all overloads of each other public void Method(B b) { ... } public void Method(C c) { ... } </code></pre> <p>Now I'm letting C# do the dispatch instead of doing it manually myself. Can this be done? The naive straightforward approach doesn't work, of course:</p> <blockquote> <p>Cannot resolve method 'Method(object)'. Candidates are:</p> <ul> <li>void Method(A)</li> <li>void Method(B)</li> <li>void Method(C)</li> </ul> </blockquote>

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