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    <p>Mostly, those restrictions are in place because of language designers. The underlying justification may be compatibility with languange history, ideals, or simplification of compiler design.</p> <p>The compiler may (and does) choose to:</p> <ul> <li>create a big if-else statement </li> <li>use a MSIL switch instruction (jump table)</li> <li>build a Generic.Dictionary&lt;string,int32&gt;, populate it on first use, and call Generic.Dictionary&lt;&gt;::TryGetValue() for a index to pass to a MSIL switch instruction (jump table) </li> <li>use a combination of if-elses &amp; MSIL "switch" jumps</li> </ul> <p>The switch statement IS NOT a constant time branch. The compiler may find short-cuts (using hash buckets, etc), but more complicated cases will generate more complicated MSIL code with some cases branching out earlier than others. </p> <p>To handle the String case, the compiler will end up (at some point) using a.Equals(b) (and possibly a.GetHashCode() ). I think it would be trival for the compiler to use any object that satisfies these constraints.</p> <p>As for the need for static case expressions... some of those optimisations (hashing, caching, etc) would not be available if the case expressions weren't deterministic. But we've already seen that sometimes the compiler just picks the simplistic if-else-if-else road anyway...</p> <p>Edit: <a href="https://stackoverflow.com/questions/44905/c-switch-statement-limitations-why#44918">lomaxx</a> - Your understanding of the "typeof" operator is not correct. The "typeof" operator is used to obtain the System.Type object for a type (nothing to do with its supertypes or interfaces). Checking run-time compatibility of an object with a given type is the "is" operator's job. The use of "typeof" here to express an object is irrelevant.</p>
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