I would like to know if I bind the TextChanged event handler to a TextBox control, then how can I ensure that won’t be allowed to bind this event handler again?
I would like to know if I bind the TextChanged event handler to a
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I would like to know if I bind the TextChanged event handler to a TextBox control, then how can I ensure that won’t be allowed to bind this event handler again?
You can’t ensure that. You would theoretically be allowed to bind the same event handler to a textbox (or other control) more than once. The only thing that events allow you to do is add a handler and remove a handler—there’s no additional means provided to check for existing subscribers. If you don’t believe me, Jon Skeet provides the authoritative answer here, and in his article on events.
If you need to ensure that you don’t accidentally subscribe a control to the same event twice, you’ll need to keep track of it yourself. Honestly, you should never end up in a situation where you don’t know what event handlers are subscribed. Not only does this reflect sloppy design, but it probably also means that you aren’t taking care to remove your event handlers when they are no longer necessary.
A possible solution is provided in the answers to this question, but I caution you from using something like this blindly. As others have argued, this code is something of an anti-pattern.