C# .NET Programming Tip: FlowLayoutPanel Mouse Scroll Wheel Not Working

Ahh, some if you may notice that the mouse scroll wheel doesn’t work by default with FlowLayoutPanels. Yeah, this little thing has frustrated me for a while.

I usually check the Internet for solutions to problems I have been having. Most likely someone has posted on a message board about the same problem and the problem was solved. Sadly, this method of finding information can lead to numerous dead ends as people don’t post the solution (eg: “Hey I figured it out!”) and fail to say what they did. Or the solution they figure out isn’t “good.” Of course, programming blogs are also a good resource with generally higher quality information, but they don’t seem to be as prevalent in search engines for some reason. Maybe blogs are generally lower traffic?

Like I said before, one such issue I was having was with FlowLayoutPanels and the mouse scroll wheel not scrolling them when the panels had scroll bars. Doing a search on the internet came up with close to nothing. Most “solutions” were to create your own functions to catch MouseEventArgs from the Form and perform the scroll on the FlowLayoutPanel yourself with scrolling code. Far from the best solution…

It didn’t make sense. The panels have all of the events necessary to scroll themselves, but they were not working. Then I came into some luck and found someone talking about the same problem I was having. They suggested that the FlowLayoutPanels were not able to get focus, so that’s why they would not scroll. Pure genius! They added one line of code to the Click event to whatever panel they wanted to scroll. Not really ideal as the user would have to know to click on the panel before they could scroll it. I took it one step further. Check out the code below.

private void newCheckListQuestionPanel_Click(object sender, EventArgs e)
{
   newCheckListQuestionPanel.Focus(); //allows the mouse wheel to work after the panel is clicked
}
private void newCheckListQuestionPanel_MouseEnter(object sender, EventArgs e)
{
   newCheckListQuestionPanel.Focus(); //allows the mouse wheel to work after the panel has had the mouse move over it
}

In Visual Studio, select the panel in the visual design window, and click the Events button in the properties window to find a list of events the control can do. I added events for Click and MouseEnter. Click probably isn’t necessary, as MouseEnter is really the star of the show here. Everytime the user moves the mouse over the FlowLayoutPanel, the control receives focus, allowing the mouse wheel to work!

Yeah, it’s that simple.

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