Question

Here’s the scenario:
Platform: Windows
IDE: Microsoft Visual Studio 2008
Language: C#
.NET framework: 3.5

My application contains 2 buttons – “Load Data” and “Stop Loading Data” and a multi-line textbox. Upon clicking “Load Data” button some data starts getting loaded in the textbox. To prevent the user clicking on the “Load Data” button multiple times, I have disabled that button once it is clicked. When the entire data gets loaded in the textbox then the “Load Data” button gets activated again. On the other hand on clicking “Stop Loading Data” button the loading of data is stopped (if user wishes to stop it before loading the entire content).
As stated earlier, to prevent the user clicking on the “Load Data” button multiple times, I have disabled that button with the intention that user can only click on “Stop Loading Data” button or else wait for the entire data to be loaded in the textbox. I implemented this. At first glance it seemed to work well. But while testing I found that even though the “Load Data” button is disabled, if the user clicks on that button, although nothing happens at that instant but as soon as the entire data gets loaded and the button becomes enabled again, that click made during the disabled state is found to be executed. As if the program was recording the keystrokes and mouse clicks and waiting for the button to become active again. But there are no such keystrokes or mouse-clicks recording facility in my program. What is causing such an activity? How can I prevent such behavior?

Thanks.

Answer 1

One option would be to work with a reentrancy sentinel:

You could define an int field (initialize with 0) and update it via Interlocked.Increment on entering the method and only proceed if it is 1. At the end just do a Interlocked.Decrement.

To make it visible for the user you can disable the button at the beginning of execution and enable it when the execution is finished…

BTW: long-running tasks should be done async (via a separate thread for example)…