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    <p>I did some tests (in .Net 3.5... later I will check at home using .Net 4). The fact is: Getting an object as an interface and then executing the method is faster than getting a delegate from a method then calling the delegate.</p> <p>Considering the variable is already in the right type (interface or delegate) and simple invoking it makes the delegate win.</p> <p>For some reason, getting a delegate over an interface method (maybe over any virtual method) is MUCH slower.</p> <p>And, considering there are cases when we simple can't pre-store the delegate (like in Dispatches, for example), that may justify why interfaces are faster.</p> <p>Here are the results:</p> <p>To get real results, compile this in Release mode and run it outside Visual Studio.</p> <blockquote> <p>Checking direct calls twice<br> 00:00:00.5834988<br> 00:00:00.5997071</p> <p>Checking interface calls, getting the interface at every call<br> 00:00:05.8998212</p> <p>Checking interface calls, getting the interface once<br> 00:00:05.3163224</p> <p>Checking Action (delegate) calls, getting the action at every call<br> 00:00:17.1807980</p> <p>Checking Action (delegate) calls, getting the Action once<br> 00:00:05.3163224</p> <p>Checking Action (delegate) over an interface method, getting both at every call<br> 00:03:50.7326056</p> <p>Checking Action (delegate) over an interface method, getting the interface once, the delegate at every call<br> 00:03:48.9141438</p> <p>Checking Action (delegate) over an interface method, getting both once<br> 00:00:04.0036530</p> </blockquote> <p>As you can see, the direct calls are really fast. Storing the interface or delegate before, and then only calling it is really fast. But having to get a delegate is slower than having to get an interface. Having to get a delegate over an interface method (or virtual method, not sure) is really slow (compare the 5 seconds of getting an object as an interface to the almost 4 minutes of doing the same to get the action).</p> <p>The code that generated those results is here:</p> <pre><code>using System; namespace ActionVersusInterface { public interface IRunnable { void Run(); } public sealed class Runnable: IRunnable { public void Run() { } } class Program { private const int COUNT = 1700000000; static void Main(string[] args) { var r = new Runnable(); Console.WriteLine("To get real results, compile this in Release mode and"); Console.WriteLine("run it outside Visual Studio."); Console.WriteLine(); Console.WriteLine("Checking direct calls twice"); { DateTime begin = DateTime.Now; for (int i = 0; i &lt; COUNT; i++) { r.Run(); } DateTime end = DateTime.Now; Console.WriteLine(end - begin); } { DateTime begin = DateTime.Now; for (int i = 0; i &lt; COUNT; i++) { r.Run(); } DateTime end = DateTime.Now; Console.WriteLine(end - begin); } Console.WriteLine(); Console.WriteLine("Checking interface calls, getting the interface at every call"); { DateTime begin = DateTime.Now; for (int i = 0; i &lt; COUNT; i++) { IRunnable interf = r; interf.Run(); } DateTime end = DateTime.Now; Console.WriteLine(end - begin); } Console.WriteLine(); Console.WriteLine("Checking interface calls, getting the interface once"); { DateTime begin = DateTime.Now; IRunnable interf = r; for (int i = 0; i &lt; COUNT; i++) { interf.Run(); } DateTime end = DateTime.Now; Console.WriteLine(end - begin); } Console.WriteLine(); Console.WriteLine("Checking Action (delegate) calls, getting the action at every call"); { DateTime begin = DateTime.Now; for (int i = 0; i &lt; COUNT; i++) { Action a = r.Run; a(); } DateTime end = DateTime.Now; Console.WriteLine(end - begin); } Console.WriteLine(); Console.WriteLine("Checking Action (delegate) calls, getting the Action once"); { DateTime begin = DateTime.Now; Action a = r.Run; for (int i = 0; i &lt; COUNT; i++) { a(); } DateTime end = DateTime.Now; Console.WriteLine(end - begin); } Console.WriteLine(); Console.WriteLine("Checking Action (delegate) over an interface method, getting both at every call"); { DateTime begin = DateTime.Now; for (int i = 0; i &lt; COUNT; i++) { IRunnable interf = r; Action a = interf.Run; a(); } DateTime end = DateTime.Now; Console.WriteLine(end - begin); } Console.WriteLine(); Console.WriteLine("Checking Action (delegate) over an interface method, getting the interface once, the delegate at every call"); { DateTime begin = DateTime.Now; IRunnable interf = r; for (int i = 0; i &lt; COUNT; i++) { Action a = interf.Run; a(); } DateTime end = DateTime.Now; Console.WriteLine(end - begin); } Console.WriteLine(); Console.WriteLine("Checking Action (delegate) over an interface method, getting both once"); { DateTime begin = DateTime.Now; IRunnable interf = r; Action a = interf.Run; for (int i = 0; i &lt; COUNT; i++) { a(); } DateTime end = DateTime.Now; Console.WriteLine(end - begin); } Console.ReadLine(); } } } </code></pre>
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    1. POPerformance of calling delegates vs methods
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    1. USPaulo Zemek
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    1. COYou probably shouldn't include getting the delegate in the time it takes to run it.
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      1. USTamusJRoyce
    2. COYou should also use the [Stopwatch class](http://msdn.microsoft.com/en-us/library/system.diagnostics.stopwatch(v=vs.110).aspx) instead of DateTime. Eric Lippert goes into [more detail](http://tech.pro/tutorial/1295/c-performance-benchmark-mistakes-part-two).
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      1. USFriendlyGuy
 

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