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POExample : Speeding up Reflection API with delegate in .NET/C#
 

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    <p>As is asked in this <a href="https://stackoverflow.com/questions/6430479/speeding-up-reflection-api-with-delegate-in-net-c/6430561#6430561">post</a>, I came up with an example that uses Delegate to speedup Refection in .NET/C#.</p> <p>However, I got this error when running (compilation works fine). What might be wrong?</p> <pre><code>Unhandled Exception: System.ArgumentException: type is not a subclass of Multicastdelegate at System.Delegate.CreateDelegate (System.Type type, System.Object firstArgument, System.Reflection.MethodInfo method, Boolean throwOnBindFailure, Boolean allowClosed) [0x00000] in &lt;filename unknown&gt;:0 at System.Delegate.CreateDelegate (System.Type type, System.Reflection.MethodInfo method, Boolean throwOnBindFailure) [0x00000] in &lt;filename unknown&gt;:0 at System.Delegate.CreateDelegate (System.Type type, System.Reflection.MethodInfo method) [0x00000] in &lt;filename unknown&gt;:0 at EX.RefTest.DelegateTest () [0x00000] in &lt;filename unknown&gt;:0 at EX.RefTest.Main () [0x00000] in &lt;filename unknown&gt;:0 </code></pre> <h2>ADDED</h2> <p>This is the (working) source code thanks to the help from Jon &amp; ChaosPandion.</p> <pre><code>using System.Reflection; using System; namespace EX { public class Hello { // properties public int Valx {get; set;} public int Valy {get; set;} public Hello() { Valx = 10; Valy = 20; } public int Sum(int x, int y) { Valx = x; Valy = y; return (Valx + Valy); } } public class RefTest { static void DelegateTest() { Hello h = new Hello(); Type type = h.GetType(); MethodInfo m = type.GetMethod("Sum"); // Wrong! Delegate call = Delegate.CreateDelegate(type, m); Delegate call = Delegate.CreateDelegate(typeof(Func&lt;int, int, int&gt;), h, m); int res = (int) call.DynamicInvoke(new object[] {100, 200}); Console.WriteLine("{0}", res); // This is a direct method implementation from Jon's post, and this is much faster Func&lt;int, int, int&gt; sum = (Func&lt;int, int, int&gt;) Delegate.CreateDelegate(typeof(Func&lt;int, int, int&gt;), h, m); res = sum(100, 200); Console.WriteLine("{0}", res); } static void Main() { DelegateTest(); } } } </code></pre> <h2>ADDED2</h2> <p>Based on Jon's answer, I did some performance test to use sum 1000 time. Compared to the method of using <code>(int) call.DynamicInvoke(new object[] {100, 200});</code>, <code>Func&lt;int, int, int&gt; sum = (Func&lt;int, int, int&gt;) Delegate.CreateDelegate(typeof(Func&lt;int, int, int&gt;), h, m);</code> is 300 times faster. </p>
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