Why is the Winforms Click event slower than the MouseClick event?

Question

I'm adding buttons to form with loop and i noticed adding click event handlers slowing down application too much. Later i tried mouse click event instead click event and it is working instantly.

This screenshot showing my test result: Source code: http://pastebin.com/qVewNm1u

Results for 1000 event handler:
Click: 2892ms MouseClick: 1ms

I can't figure out why Click event very slow.

Edit: If i change build platform target to x64 or Any CPU, results changing: Click: 5, MouseClick: 9 Look like x86 platform target causing this problem but still x64 results not good too compared to x86 MouseClick time (1ms).

Edit2: I changed screenshot now it will show better result.

Edit3: https://connect.microsoft.com/VisualStudio/feedback/details/597039/winforms-click-event-slower-than-the-mouseclick-event

Answer 1

Have you tried creating the buttons first, before measuring the event handler attachment?

There are at least two unknowns here: 1) the button constructor execution time, and 2) the event handler subscription.

Update: I tried to reproduce the problem but I consistently get 4ms-6ms for both tests. Is the one test always slower, or did it happen just once? Sometimes weird things happen with jitting and GCing that aren't always 100% deterministic.

Answer 2

While I can't tell you what's going on, there are a number of problems with your test suite.

First, you should probably stop the timer before doing the Console.WriteLine, since you are now also measuring how long it takes to create the string used in the WriteLine.

Second, you may want to create the buttons before starting the timer, because you're also measuring the button creation time, which includes stack, heap, garbage collection, and other potential issues. I'd suggest allocating the buttons to an array, then assigning the even handlers to the items after you start the stopwatch.

Answer 3

I am not sure because I have only a small 4ms for ClickTest(). However, I have change the code to this and the 4ms time is gone.

EventHandler d = new EventHandler(Form1_Click);
for (int i = 0; i < buttons.Length; i++) buttons[i].Click += d;

The code in the loop you wrote are equivalent to button[i].Click += new EventHander(Form_Click), which create new delegate instance on every iteration.

Answer 4

I repro, but it is specific to VS2010. There is no such behavior in VS2008, both execute in less than 1 tick. It also doesn't depend on the .NET version.

This looks like a defect in IntelliTrace, available in the Ultimate edition. Trying to dig deeper and turning unmanaged code debugging on removed the effect. Project + Properties, Debug tab, tick "Enable unmanaged code debugging". Also, running the program without the debugger (Ctrl+F5) removed the effect. The slam-dunk is Tools + Options, IntelliTrace, General, untick Enable to remove the effect.

I recommend you post your findings to connect.microsoft.com. You can reference this thread in your feedback report. Everything they need to know to diagnose the problem is available.

As noted, the workaround is to disable IntelliTrace. This is guaranteed to not be a problem on your customer's machine.