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POCasting ints to enums in C#
 

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    <p>There is something that I cannot understand in C#. You can cast an out-of-range <code>int</code> into an <code>enum</code> and the compiler does not flinch. Imagine this <code>enum</code>:</p> <pre><code>enum Colour { Red = 1, Green = 2, Blue = 3 } </code></pre> <p>Now, if you write:</p> <pre><code>Colour eco; eco = (Colour)17; </code></pre> <p>The compiler thinks that’s fine. And the runtime, too. Uh?</p> <p>Why did the C# team decide to make this possible? This decision misses the point of using enums, I think, in scenarios like this:</p> <pre><code>void DoSomethingWithColour(Colour eco) { //do something to eco. } </code></pre> <p>In a strong-typed language like C#, I would like to assume that <code>eco</code> will always hold a legal <code>Colour</code> value. But this is not the case. A programmer could call my method with a value of 17 assigned to <code>eco</code> (as in previous code snippet), so the code in my method must not assume that <code>eco</code> holds a legal <code>Colour</code> value. I need to test for it explicitly and handle the exceptional values as I please. Why is this?</p> <p>In my humble opinion, it would be much nicer if the compiler issued an error (or even a warning) message when casting an out-of range <code>int</code> into an <code>enum</code>, if the <code>int</code> value is known at compile time. If not, the runtime should throw an exception at the assignment statement.</p> <p>What do you think? Is there any reason why this is so?</p> <p>(Note. This is a question <a href="http://neh2.wordpress.com/2004/12/13/casting-enums-into-ints/" rel="noreferrer">I posted ages ago on my blog</a> but got no informative response.)</p>
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