[C#] Problem with double-click on ListBox item

1,567 · September 13, 2008

Hi there,

I have a ListBox with a few items and at sometimes, when the ListBox only has a couple of items, you'll see a blank area after the last item because there are no more items to fill the ListBox.

Now, I've implemented the MouseDoubleClick event to get the index of the double-clicked item in the ListBox like this:

private void listNotes_MouseDoubleClick(object sender, MouseEventArgs e) {
	int noteIndex = listNotes.IndexFromPoint(e.Location);

	// DO SOMETHING ELSE...
}

However, if I double-click on that blank area, noteIndex will have the index value of the last item on the list.

I need to ignore this behavior. Any suggestions?

2,595 · September 13, 2008

Just use .SelectedIndex?

if comes back as -1 then there is no item selected.

Cheers,

MiG

1,567 · September 13, 2008

You are right about something, SelectedIndex is much simpler. I don't know why I didn't use it in the first place... However, it does not solve the problem.

Double-clicking the blank area will return the index from the last item in the ListBox. Forget for a minute about the double-clicking, because that's not probably the problem. Let's say that event is not implemented, when you single-click any item in the ListBox, that item will be selected, but if you single-click on the blank area below the last item, that last item will be selected.

Conclusion, the last item is being selected when I click on the blank area, that's what I want to avoid...

8,405 · September 13, 2008

Coud it be the way you are adding items on the ListBox?

1,567 · September 13, 2008

I'm using: listNotes.Items.Add()

1,567 · September 14, 2008

I guess it's a default behavior that can't be changed :/

4,003 · September 14, 2008

Nazgulled said:
I guess it's a default behavior that can't be changed :/

It is a default behaviour, but you can code an event handler that is triggered on a double click to combat your issue.

Thanks

2,595 · September 14, 2008

Nazgulled said:
You are right about something, SelectedIndex is much simpler. I don't know why I didn't use it in the first place... However, it does not solve the problem.
Double-clicking the blank area will return the index from the last item in the ListBox. Forget for a minute about the double-clicking, because that's not probably the problem. Let's say that event is not implemented, when you single-click any item in the ListBox, that item will be selected, but if you single-click on the blank area below the last item, that last item will be selected.

Conclusion, the last item is being selected when I click on the blank area, that's what I want to avoid...

If I click the blank region in a listbox the last item is not selected and the selectedIndex returns -1. If there is a item selected from a previous single click then that selected index will be returned because it is the item selected, and the double click is based on clicking the listbox.

ways around would be to clear the Selected Items before you get the selectedIndex. make a copy of them before, and then re-assign them after you get the selectedIndex from the mouseClick.

That way, no interference from other events should be a problem.

1,567 · September 14, 2008

I don't understand what you are saying.

I cleared the selected items, clicked the blank area and the last item was selected...

One thing I haven't told you and maybe that's where is the problem... I'm using the KryptonListBox from the Krypton Toolkit, not the ListBox from Windows Forms. Maybe I should post this on the Krypton forums...

Thanks for all your help :)

2,595 · September 14, 2008

Nazgulled said:
I don't understand what you are saying.
I cleared the selected items, clicked the blank area and the last item was selected...

One thing I haven't told you and maybe that's where is the problem... I'm using the KryptonListBox from the Krypton Toolkit, not the ListBox from Windows Forms. Maybe I should post this on the Krypton forums...

Thanks for all your help :)

From what I understand, you were saying that clicking a the blank area in the Listbox selects the last item. I can't recreate this behaviour using the 2008 Windows Forms version. Whether the Krypton one adds this is something to investigate.

The main problem I understand is that the double click event works, just that other event handlers and functions are getting in the way, such as single click, ect. To rectify this the only way I can think of would be to save the state of the object before the click, then clear down all selected properties, and just look at the one from the MouseEventArgs.

Then you can copy the data back in. That way, any items selected before the double click will be ignored. Of course this is catering for a very small number of possibilities..

1,567 · September 14, 2008

I don't really know what to say...

Please take a look at the attached solution. It's a very simple C# app with just the KryptonListBox. Open it, press F5 and click on the blank area. You'll see the last item getting selected...

WindowsFormsApplication1.zipFetching info...

9,364 · September 14, 2008

Nazgulled said:
I don't really know what to say...
Please take a look at the attached solution. It's a very simple C# app with just the KryptonListBox. Open it, press F5 and click on the blank area. You'll see the last item getting selected...

Not played with C# for a while, but wouldn't you be able to hook into the ondoubleclick event on the items themselves, thus avoiding this issue?

2,595 · September 14, 2008

DaveLegg said:
Not played with C# for a while, but wouldn't you be able to hook into the ondoubleclick event on the items themselves, thus avoiding this issue?

I tried to do this earlier but I don't its possible in C#. Played with the attached solution as well and can't really get anywhere with it.

8,405 · September 14, 2008

Oh its an custom made listbox. I played with it and the same happens so I changed "SelectionMode" to None and it works... and it doesnt. MouseDoubleClick event doesnt work only SelectedIndexChanged. I guess the creator of the control left some things out.

1,567 · September 14, 2008

You are saying I should take this to the creator of the control then instead of trying to find a workaround?

5,526 · September 15, 2008

I'm not sure what exactly is going on, but I tried a simple project with a listbox, a few items and subscribed to the MouseDoubleClick event, and this worked fine;

MessageBox.Show(listBox1.IndexFromPoint(e.Location).ToString());

Which is what you were using earlier, and it works on my machine. Regardless of previously selected items, if you double click in the extra space in the listbox (the area not occupied by a list item), it successfully returns -1 :s

1,567 · September 15, 2008

@Antaris

Please try that on the test solution I provided in post #11 if you have the time...

1,567 · September 16, 2008

The author of Krypton Toolkit answered me with this:

"Phil Wright" said:
I think the difference in behavior is because the Krypton list box is owner drawn and your standard one is not. But you can use code to work out the answer. Compare the returned item with the display rectangle of that item to ensure it really is under the mouse...
		private void kryptonListBox1_MouseDoubleClick(object sender, MouseEventArgs e)
		{
			int noteIndex = kryptonListBox1.IndexFromPoint(e.Location);
			if ((noteIndex &gt;= 0) &amp;&amp; (!kryptonListBox1.GetItemRectangle(noteIndex).Contains(e.Location)))
				noteIndex = -1;
		}

That would work for the MouseDoubleClick but I also have some buttons that perform actions on the selected listbox item. A single mouse click on the blank area also selects the last item. I also need to ignore this behavior... I've been trying a couple of things around the code above but haven't managed to do so, any ideas?

1,567 · September 17, 2008

No one has any more ideas?

5,526 · September 17, 2008

The problem is, that the selection code occurs within Krypton library, not at your form level. Can you override any virtual methods to control the selection process?

1,567 · September 18, 2008

I can override some if I created a class based on KryptonListBox, actually, already tried this but couldn't find a method that would help me with this problem, or I'm seeing how could I use that method to work around the problem...

1,567 · September 18, 2008

The problem is now fixed.

If anyone is interested in the solution, please take a look here:

http://www.componentfactory.com/forums/vie...?f=3&t=1516

It's a workaround that Chris Porter suggested me there...

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[C#] Problem with double-click on ListBox item

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