Combox SelectedIndexChanged fires when close the WinForm

Question

I am using Combobox SelectedIndexChanged event to perform few tasks. It is working nice. But when i am closing the form, SelectedIndexChanged gets fired and i get "Object reference not set to an instance of an object." exception. My code is following-

    private void cmbProductName_SelectedIndexChanged(object sender, EventArgs e)
    {
        try
        {
            Product p =(Product) cmbProductName.SelectedItem;

            RawItems = RawItem.GetEntityList(p.Id, ConnectionString);

        }
        catch (Exception ex)
        {
            CustomMessageBox.ShowSystemException(ex);
        }
    }

How to avoid the SelectedIndexChanged event being fired when form is closing?

Thanks SKPaul.

anything your setting related to cmbProductName in Form Closing event? or may be focus will be there in Combo. — andy, Nov 06 '12 at 11:15
firing Combobox SelectedIndexChanged on closing not a normal behavior than be sure you not call it when closing — Akrem, Nov 06 '12 at 11:22

sohel khalifa · Accepted Answer · 2012-11-06T12:31:51.970

8

If you want to perform the tasks only when user change selected item in combo box, it is better to implement the SelectionChangeCommitted event

[EDIT]

According to MSDN docs SelectionChangeCommitted occurs only when the ComboBox selection changes by user (via keyboard or mouse) and it is not raised when the selection changes programmatically.

When a value is changed in the list, SelectionChangeCommitted event is fired first and then SelectedIndexChanged event is fired.

So if we need to do anything on SelectedIndexChanged, we can remove it and do the same work in SelectionChangeCommitted event handler.

Simply handle this event instead of SelectedIndexChanged as below:

private void cmbProductName_SelectionChangeCommitted(object sender, EventArgs e)
{
    /*
      Your event handling code
    */
}

edited Nov 06 '12 at 12:31

answered Nov 06 '12 at 11:17

sohel khalifa

5,602
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This is a good idea. But i have never use this event. I have to study it. But i would be grateful if you post a tiny example. – s.k.paul Nov 06 '12 at 12:18
Thanks Khalifa. How can i satisfy you ? 10 out of 10 ?? ha haha. I am going to change my code.Thanks again. – s.k.paul Nov 06 '12 at 12:43
SelectionChangeCommitted creating problems. – s.k.paul Nov 06 '12 at 16:40

score 5 · Answer 2 · answered Nov 06 '12 at 11:14

5

Try unregistering the event in the FormClosing event handler:

MyComboBox.SelectedIndexChanged -= combox_SelectedIndexChanged;

answered Nov 06 '12 at 11:14

Laila

417
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score 2 · Answer 3 · edited May 23 '17 at 12:23

2

During the from closing you can remove ComboBox event handler. Therefore you need Closing event handler for your form and there you must remove cmbProductName_SelectedIndexChanged callback.

Here you can read about Form.Closing and how to remove event handler.

edited May 23 '17 at 12:23

Community

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answered Nov 06 '12 at 11:14

besworland

747
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17

Combox SelectedIndexChanged fires when close the WinForm

3 Answers3

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