How to prevent a ComboBox from firing another ComboBox's SelectedIndexChanged event when filling it

Question

So, basically I'm using a ComboBox.SelectedIndexChanged event to fill 5 more ComboBoxs wich each have their own SelectedIndexChanged event as well.

The problem is that when the first SelectedIndexChanged event fires to fill the rest.. it also fires the other ComboBoxes' SelectedIndexChanged event.

In order to prevent that, I have found a solution using the event SelectionChangeCommited on the rest of the ComboBoxes.

But now, that event (unlike SelectedIndexChanged) doesn't fire on the first click on the item of the ComboBox... you need to select the item two or three times before it does.

So, my question is: is there any way to fix these problems?

If the child combobox `SelectedIndex` property changes to -1 when the parent `selectionChanged` fires you could parse out when to take action. I think when nothing is selected the `SelectedIndex` goes to -1. So essentially ignore` Selectedindex = -1` — Felix Castor, Mar 05 '16 at 16:21

score 1 · Answer 1 · answered Mar 05 '16 at 16:25

1

In code, before you 'fill' the secondary comboboxes, unsubscribe from their SelectedIndexChanged event, then re-subscribe when the 'fill' code has run

answered Mar 05 '16 at 16:25

Dean Chalk

20,076
6
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Thank you for your answer, I do find it intresting, Could you please give me an example on how to do that? – OumasAbdellah Mar 05 '16 at 19:33

Antonín Lejsek · Accepted Answer · 2016-03-06T00:05:25.730

0

I would make local variable and set it for the time the SelectedIndexChanged should be ignored

protected bool ignoreSelectedIndexChanged = false;

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    if (ignoreSelectedIndexChanged) { return; }

    //rest of code
}

it seems to me more explicit than fiddling with the events.

In the main ComboBox use something like:

private void comboBoxMain_SelectedIndexChanged(object sender, EventArgs e)
{            
    try
    {
        ignoreSelectedIndexChanged = true;

        //comboBox1.SelectedIndex = 1;
        //comboBox2.SelectedIndex = 2;
        //comboBox3.SelectedIndex = 3;
        //...

    }
    finally
    {
        ignoreSelectedIndexChanged = false;
    }
}

SelectionChangedCommited may be another way how to do it. But it is fired only when user does the selection, what may be limiting for some cases. And there were dome bugs of not firing when it should. I personally avoid it.

edited Mar 06 '16 at 00:05

answered Mar 05 '16 at 17:33

Antonín Lejsek

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2
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Thank you for the answer, in this case should I just forget about the SelectionChangedCommited event or will the SelectedIndexChanged event work ? – OumasAbdellah Mar 05 '16 at 19:36
@watchDogMan I added more explanation if it helps. – Antonín Lejsek Mar 06 '16 at 00:06
It worked very well, Thanks again, easy solution, never thought of it tho (y) – OumasAbdellah Mar 06 '16 at 12:12

Kevin Villasana · Answer 3 · 2016-03-07T15:07:26.133

Using a flag, for example
in case you only have 2 combo boxes

int flag =0;

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    switch(flag)
    {
       case 0:
           flag = 1;
       break;

       case 1:
           // your code here
           // after it you should set flag = 0
       break;

       default:
       break;
    }

}

private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)
{

    switch(flag)
    {
       case 0:
           flag = 2;
       break;

       case 2:
           // your code here
           // after it you should set flag = 0
       break;

       default:
       break;
    }        
}

and just like that depending on the number of comboboxes you're using.

How to prevent a ComboBox from firing another ComboBox's SelectedIndexChanged event when filling it

3 Answers3