How costly is .NET reflection?


I constantly hear how bad reflection is to use. While I generally avoid reflection and rarely find situations where it is impossible to solve my problem without it, I was wondering...

For those who have used reflection in applications, have you measured performance hits and, is it really so bad?

10/22/2011 9:49:06 AM

Accepted Answer

It is. But that depends on what you're trying to do.

I use reflection to dynamically load assemblies (plugins) and its performance "penalty" is not a problem, since the operation is something I do during startup of the application.

However, if you're reflecting inside a series of nested loops with reflection calls on each, I'd say you should revisit your code :)

For "a couple of time" operations, reflection is perfectly acceptable and you won't notice any delay or problem with it. It's a very powerful mechanism and it is even used by .NET, so I don't see why you shouldn't give it a try.

8/24/2008 11:48:33 PM

In his talk The Performance of Everyday Things, Jeff Richter shows that calling a method by reflection is about 1000 times slower than calling it normally.

Jeff's tip: if you need to call the method multiple times, use reflection once to find it, then assign it to a delegate, and then call the delegate.

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