Best way to handle double-click buttons in a winforms app?

Question

I am working on a WinForms application and I have a user control. Buttons in a user control raise events to a form processed by another code. One of the buttons starts some processes that will cause problems if they run simultaneously. I have logic in the code for state management, so usually the user cannot start this process if it is already running. However, if the user double-clicks the button, he will start the process twice so quickly that it is difficult for me to prevent it.

I am wondering what is the best way to handle this?

I started by turning off the button in the click event, but the second click appears before the first click, which causes the button to turn off. Setting other flags in the code also did not catch it.

I am considering adding some kind of synchronization lock to the code that triggers the event, but I am wondering if you have any better idea.

Since this project is mostly finished, I am looking for answers that are not related to a radical rewrite of the application (for example, implementing a composite block of applications), however, do not hesitate to publish these ideas, as I can use them in my next projects.

Answer 1

Make sure your button is disabled or any other lock you make is / first / thing that you do in the event handler. I would be very surprised if you could queue two click events before even the first command fires, but I believe that this is possible if you are on a very slow computer that is bogged down with other applications.

In this case, use the flag.

private bool runningExclusiveProcess = false; public void onClickHandler(object sender, EventArgs e) { if (!runningExclusiveProcess) { runningExclusiveProcess = true; myButton.Enabled = false; // Do super secret stuff here // If your task is synchronous, then undo your flag here: runningExclusiveProcess = false; myButton.Enabled = true; } } // Otherwise, if your task is asynchronous with a callback, then undo your flag here: public void taskCompletedCallback() { runningExclusiveProcess = false; myButton.Enabled = true; } 

If you can still make two clicks on something similar, make sure that you are not accidentally subscribing to the doubleClick event or something else is inactive.

Answer 2

Do you handle the event twice?

I am very surprised to learn that the second click is coming before you can disable the button. I would like to make sure you are not connecting the event twice. I used to do this by accident. After that, you will receive two events almost instantly.

Answer 3

The disable flag on this button will not be set until the button's event handler completes and any additional clicks are queued in the Windows message queue with the first click. Make sure the button event handler shuts down quickly to free up the user interface thread. There are several ways to do this, but they all require that ewn create a thread or maintain a workflow and expect AutoResetEvent.

Answer 4

Disable the button after the user first clicks it and before starting the task. When the task is completed, turn on the button again.

Answer 5

Did you accidentally mark a button with an icon? By all means, use the code to prevent the two processes from starting simultaneously, but you can reduce the double-click on the person’s side if your button looks and acts like a regular command button (a rectangular, just a text label, “raised” surface that clicks on click). Just a thought.

Answer 6

Disable the button as soon as it is pressed. Therefore, the event cannot be processed twice. Once the event has been processed, you can turn on the button again.

Answer 7

A proven answer is close if it is anecdotal at best. For the uninitiated, he lacks too much code to make sense. I wrote an article about using timers and threads, and the sample code is REALLY easy to understand. Try reading it and see if you can set the flags from the above example by completing the task process in a new thread:

http://www.robault.com/category/Threading.aspx

Answer 8

I started by disabling the button in the click event, but the second click appears until the first click causes the button to lock. Setting other flags in the code do not catch it.

Given that WinForms is essentially single-threaded, it should not be possible for the second click to light up before the processing for the first is complete (unless you are using new threads or BackgroundWorkers, etc.).

Can you show us a sample illustrating your problem?