Stop comboBox's selectedIndexChanged event from firing when the form loads

Question

I have a form with a ComboBox that provides a dropdownlist. On the comboBox's SelectedIndexChanged event, am running some code, but I don't want that code to run when the form loads. Unfortunately, when I load the form (before I make a selection in the combobox), SelectedIndexChanged of the combobox fires (I think when the combobox is databinding). Is there a way of avoiding such behaviour?

Not sure about on the desktop, but in .NET Compact, this event actually appears to fire before the Form_Load event, which is really problematic - nothing on the form is even set up yet when this code gets hit. On CF, the solution is unfortunately a form variable that gets set at the end of Load, and then the event handler checks for this variable before it fires. — SqlRyan, Feb 11 '13 at 02:19

score 155 · Accepted Answer · edited Dec 28 '12 at 21:33

155

If you want to react only when the user change the selected item in the combo box, then it is better to subscribe to SelectionChangeCommitted.

edited Dec 28 '12 at 21:33

Peter Mortensen

30,738
21
105
131

answered Jul 16 '10 at 19:16

arbiter

9,447
1
32
43

6

But what to do in case of autocompete? – Arijit Mukherjee Jul 09 '14 at 10:13
@Arijit Mukherjee right. When typing a value into textbox instead of selecting directly. It won't trigger SelectionChangeCommitted event – thoitbk Jan 06 '15 at 13:08
1

Damn, I have been searching the web for quite a while to find a simple solution like this. I have been using the SelectionChanged event and it worked in VB.Net - WPF and now using it on C# - WinForms and it doesnt work or maybe it is just me. Thanks! – Stephan Aug 29 '15 at 20:58
Akams Razor - the simplest solution is the most likely (and the best in this case). – Destek Jul 30 '20 at 12:45

score 14 · Answer 2 · edited Dec 28 '12 at 20:10

14

You can simply unbind the SelectedIndexChanged event, call your fill function and bind the SelectedIndexChanged event again. Unfortunately, this doesn't work with a grid.

For example:

this.cmb.SelectionChanged -= new System.EventHandler(this.cmb_SelectionChanged);
cmb.fill(); //Your function
this.cmb.SelectionChanged += new System.EventHandler(this.cmb_SelectionChanged);

edited Dec 28 '12 at 20:10

Peter Mortensen

30,738
21
105
131

answered Jul 16 '10 at 08:50

Shantanu Gupta

20,688
54
182
286

score 11 · Answer 3 · edited Dec 13 '12 at 13:35

11

Be sure to set the DataSource property in your onload() function after assigning the ValueMember and Datamember properties.

This will help you to solve your problem!

edited Dec 13 '12 at 13:35

Akhil Jain

13,872
15
57
93

answered Dec 13 '12 at 13:08

Ranjith

111
1
2

2

Please add more info that elaborates your thinking. – Lenin Dec 13 '12 at 13:31
@Ranjith: can you elaborate? – Peter Mortensen Dec 28 '12 at 20:14
Solves the problem. Thanks but please elaborate. – hubert17 Jan 21 '19 at 19:21
Assigning a new DataSource fires a "selectedIndexChanged" event. – John Feb 09 '20 at 20:12
lol, what is this craziness =D! Thank you though! – Khaled Nov 03 '21 at 23:34
It´s perfect!. Thanks. – Javier dc Jan 06 '22 at 12:21

score 5 · Answer 4 · answered Jul 16 '10 at 19:20

5

Why not have a boolean flag that indicates when your Form has finished loading?

In your SelectionChanged event, check if the boolean flag is true. If it is true then handle the event, otherwise ignore it.

answered Jul 16 '10 at 19:20

2

booooooolean.. SelectionChangeCommitted much nicer – Piotr Kula Feb 28 '12 at 12:58
4

There is already a boolean flag ` Control.Created` telling you, that the form has finished loading, which is also valid for forms. – user1734987 Oct 12 '12 at 06:54
`ToolStripComboBox` variation does not have a `SelectionChangeCommitted` event. So, this method will have to do. Or, to prevent race conditions, use `lock` and `Monitor.TryEnter`. – spoulson May 23 '13 at 18:47
@user1734987: That's not the same thing. There could be initialization code that needs to be completed and Control.Created won't fire that. – May 23 '13 at 19:05

score 2 · Answer 5 · answered Sep 06 '20 at 09:23

2

Here is a simple solution that leaves your code almost untouched:

In the SelectedIndexChanged event, check if the myComboBox handle is created using the (IsHandleCreated) method. Another added check is to check if the user is actually focusing your combobox control to change selected index.

 private void myComboBox_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (myComboBox.IsHandleCreated &&  myComboBox.Focused)
        {
           // Do something here
        }
    }

answered Sep 06 '20 at 09:23

Mohamed Nagieb

819
9
11

You need to add a SelectedValue != null check as well to this, and then it's a perfect solution. – Mecanik May 18 '21 at 06:07
Yes, this is going to be a good added check too. – Mohamed Nagieb Jun 10 '21 at 12:53
myComboBox.Focused is usually False – Greatchap Jan 04 '22 at 14:04

score 1 · Answer 6 · edited Nov 25 '17 at 18:42

1

VB

RemoveHandler lbxNomes.SelectedIndexChanged, AddressOf lbxNomes_SelectedIndexChanged
lbxNomes.DataSource = dst
Label1.Text = String.Format("Encontrados {0} Sócios nesta pesquisa", dst.Rows.Count)
Label1.Visible = True
AddHandler lbxNomes.SelectedIndexChanged, AddressOf lbxNomes_SelectedIndexChanged

edited Nov 25 '17 at 18:42

Camilo Terevinto

31,141
6
88
120

answered Aug 17 '15 at 16:56

Paulos02

163
1
4

score -1 · Answer 7 · edited May 12 '17 at 12:22

-1

It worked for me in a way with the following code:

  private void ddlChapter_SelectionChangeCommitted(object sender, EventArgs e)
    {
        if (ddlChapter.SelectedValue != null)
        {
           // Do something here
        }
    }

edited May 12 '17 at 12:22

Peter Mortensen

30,738
21
105
131

answered Aug 04 '16 at 06:08

Anjan Kant

4,090
41
39

SelectionChangeCommitted will stop to call index change items, once all items loaded into dropbox then you can select one by one only, it will increase your loading speed also. – Anjan Kant Aug 16 '16 at 07:06

Stop comboBox's selectedIndexChanged event from firing when the form loads

7 Answers7

Linked