Overhead of try/finally in C#?

Question

We\'ve seen plenty of questions about when and why to use try/catch and try/catch/finally. And I know there\

Answer 1

Let's actually put some benchmark numbers to this. What this benchmark shows is that, indeed, the time of having a try/finally is about as small as the overhead of a call to an empty function (probably better put: "a jump to the next instruction" as the IL expert stated it above).

            static void RunTryFinallyTest()
            {
                int cnt = 10000000;

                Console.WriteLine(TryFinallyBenchmarker(cnt, false));
                Console.WriteLine(TryFinallyBenchmarker(cnt, false));
                Console.WriteLine(TryFinallyBenchmarker(cnt, false));
                Console.WriteLine(TryFinallyBenchmarker(cnt, false));
                Console.WriteLine(TryFinallyBenchmarker(cnt, false));

                Console.WriteLine(TryFinallyBenchmarker(cnt, true));
                Console.WriteLine(TryFinallyBenchmarker(cnt, true));
                Console.WriteLine(TryFinallyBenchmarker(cnt, true));
                Console.WriteLine(TryFinallyBenchmarker(cnt, true));
                Console.WriteLine(TryFinallyBenchmarker(cnt, true));

                Console.ReadKey();
            }

            static double TryFinallyBenchmarker(int count, bool useTryFinally)
            {
                int over1 = count + 1;
                int over2 = count + 2;

                if (!useTryFinally)
                {
                    var sw = Stopwatch.StartNew();
                    for (int i = 0; i < count; i++)
                    {
                        // do something so optimization doesn't ignore whole loop. 
                        if (i == over1) throw new Exception();
                        if (i == over2) throw new Exception();
                    }
                    return sw.Elapsed.TotalMilliseconds;
                }
                else
                {
                    var sw = Stopwatch.StartNew();
                    for (int i = 0; i < count; i++)
                    {
                        // do same things, just second in the finally, make sure finally is 
                        // actually doing something and not optimized out
                        try
                        {
                            if (i == over1) throw new Exception();
                        } finally
                        {
                            if (i == over2) throw new Exception();
                        }
                    }
                    return sw.Elapsed.TotalMilliseconds;
                }
            }

Result: 33,33,32,35,32 63,64,69,66,66 (milliseconds, make sure you have code optimization on)

So about 33 milliseconds overhead for the try/finally in 10 million loops.

Per try/finally then, we are talking 0.033/10000000 =

3.3 nanoseconds or 3.3 billionth of a second overhead of a try/finally.