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    <p>I haven't seen that effect - I've certainly never encountered it being a bottleneck.</p> <p>Here's a very rough-and-ready benchmark which shows (on my box anyway) delegates actually being <em>faster</em> than interfaces:</p> <pre><code>using System; using System.Diagnostics; interface IFoo { int Foo(int x); } class Program : IFoo { const int Iterations = 1000000000; public int Foo(int x) { return x * 3; } static void Main(string[] args) { int x = 3; IFoo ifoo = new Program(); Func&lt;int, int&gt; del = ifoo.Foo; // Make sure everything's JITted: ifoo.Foo(3); del(3); Stopwatch sw = Stopwatch.StartNew(); for (int i = 0; i &lt; Iterations; i++) { x = ifoo.Foo(x); } sw.Stop(); Console.WriteLine("Interface: {0}", sw.ElapsedMilliseconds); x = 3; sw = Stopwatch.StartNew(); for (int i = 0; i &lt; Iterations; i++) { x = del(x); } sw.Stop(); Console.WriteLine("Delegate: {0}", sw.ElapsedMilliseconds); } } </code></pre> <p>Results (.NET 3.5; .NET 4.0b2 is about the same):</p> <pre><code>Interface: 5068 Delegate: 4404 </code></pre> <p>Now I don't have particular faith that that means delegates are <em>really</em> faster than interfaces... but it makes me fairly convinced that they're not an order of magnitude slower. Additionally, this is doing almost nothing within the delegate/interface method. Obviously the invocation cost is going to make less and less difference as you do more and more work per call.</p> <p>One thing to be careful of is that you're not creating a new delegate several times where you'd only use a single interface instance. This <em>could</em> cause an issue as it would provoke garbage collection etc. If you're using an instance method as a delegate within a loop, you will find it more efficient to declare the delegate variable outside the loop, create a single delegate instance and reuse it. For example:</p> <pre><code>Func&lt;int, int&gt; del = myInstance.MyMethod; for (int i = 0; i &lt; 100000; i++) { MethodTakingFunc(del); } </code></pre> <p>is more efficient than:</p> <pre><code>for (int i = 0; i &lt; 100000; i++) { MethodTakingFunc(myInstance.MyMethod); } </code></pre> <p>Could this have been the problem you were seeing?</p>
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    1. COCan you elaborate on what the compiler does in the last case? Does it create a new delegate instance on every iteration or?
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    2. COWould this change if you turned it into an event using the delegate?
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    3. CO@JanJ: Check the compiled code with ildasm, but I believe it will, yes. @Chris S: Could you give more details about what you mean?
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