Is there a trick to getting a SlectedIndexChanged event to fire on a DropDownlist control?

No matter how I select an item this event does not fire.
 
I ahev checked my code, I can do even handling for any of the other controls in the form but nothing on this DropDownList.

Thansk in advance.

Hi I have the similar problem w/o the event firing for dropdownlist when i pass a function at selected change event..any further help pls!

thanx

I run into this bug occasionally. Today, I fixed it by fixing up some of the page HTML.

In my case, I had had a table nested within a table. I ended up deleting the outer table and somehow ended up with an orphan <strong> tag above my <table> tag. In the HTML window, this is underlined in red as invalid but, of course, you never see this if you are editing in Design view and just looking at that and your compiler output.

Once I deleled the bad nesting, the event fired normally.

So, start by checking your HTML.

I have had and am again havingthis same bug of ddl SelectedIndexChanged not firing.

When I select a new value on the ddl, the page posts back, the Page_Load function is invoked as PostBack, but the Event handler is never called. I have checked the handler logic in InitializeComponent; it is fine.

Yes, Autopostback is set true.

I use this event all the time. It works on most pages with no problem.

It will not work on the current page I am on, no matter what I do.

I am working in VS, .Net Framework 1.1, developing a webform. All other controls on the webform work fine - buttons, checkboxes and datagrid select.

There are no visible HTML errors on the html page.

I have no clue what else to look at or try.

I would greatly appreciate any insight or direction on where to go to get some actual help with this.

tim

Hello,

I have found that when I cut a control off of a form in design view and then paste it inside another container control (eg a GroupBox) that the Handles clause of my pre-existing event code gets stripped off. Since that is at the end of the method declaration, I usually end up pulling my hair out for a while until I think to check that.

I too was experiencing what others have reported - the postback occurs, but the SelectedIndexChanged event is not called.

I think I've found a definitive cause for this and a workaround.

It seems that this event will only fire if the Value propertychanges. A bit of a bummer if you want different items to return the same value. (I got into this because the same timezone is called different things in different parts of the world.)

The"quick and dirty" code fragments below showthe workaround

To load the list (unbound)

N = 0
While dr.Read 'dr is a DataReader
lstTimezones.Value = N.ToString & "|" & dr(0)
... additional code
N = N +1
End While

In the SelectedIndexChanged event:

ValueSplit()As String = Split(lstTimezones.SelectedValue,"|")
TimezoneCode = ValueSplit(1)

Is this an HTML thing or a Microsoft thing? I'd be interested in knowing.

Hi,

I had the same kind of problem. Hema's solution worked out.

Thanks,

Chakri.

I had the same problem but whenI made auto postback property true, it worked

Thanks

Sree

Oh !!

hours of testing and i was finally able to figure this out.

I had EnableViewState turned off with my .aspx page header.

when the ViewState is not saved it reverts back to the First Item as the Selected Index. Selecting the First Item then does not trigger a SelectedIndexChange Event.

make sure EnableViewState is true both on the control and on the page.

Manpreet.

ya Manpreet's solution works fine .............

even I was facing the same problem & enabling Viewstate Works through it..

ThanxAll :-)..

Inderdeep..

I also had the same prob ... now its fine..

Same problem here. SelectedIndexChanged was not firing after initial page load. Everything OK after one Page postback ???

:::: Finally solved this by removing something called "EnableSmartPaging=true" (or something very similar) in the aspx page header.

took me 4 hours to find this one....

I met the similar problemwhen I was creating the user control which contains a ddl.

In testing, i found that the ddl can't postback the value I selected. I checked ViewState is set ture.

What's funny is that I have another user control with the same code and same entironment, that one works fine...

And, I put the control into another test page, it works fine also -.-

Now the problem seems to be fixed, but I don't knowwhy and whether it will occur again or not...

God bless me...

I had the same problem, and after 5 long hours i found the solution.

For theSelectedIndexChanged to be triggered, the drop down that triggers it has to have the same ID before and after the postback. Now, if you create the drop down list in the server side and do not give it an ID, then it would get an ID automatically from the .NET. The problem is when the ID it gets after the postback is not the same ID it got before the postback. This could be due to many things.

the solution: ddlSomething.ID = "ddlSomething";

Jeeesshhhh!

That took a while to find!

Fixed it with:

DropDownList ddTPS = new DropDownList();

foreach (DataRow dr in TPSData.Rows)

ddTPS.Items.Add(new ListItem(dr["TPS"].ToString(), i /*Be sure this the PkId or a unique value "*/ );

i++;

OK. I did everything that everyone in the forum said. Set autopostback="true" on ddls. EnabledViewState everywhere. Set AutoEventWireUp="true" at page level.

Nada folks. Since the value on each item is the same, in this case blank. It would not fire.

My solution was as follows.

Sheesh. 4-5 hours on this. What a waste.

Thanks a lot Friends,

Solved the problem by setting AutoPostBack value to TRUE in DROP DOWNLIST PROPERTIES.

I had an issue with DropDown's not firing events when I put them on a page that had a Master page. If I got rid of the Master page the events worked fine.Turns outwe had some vbscript in the header of the Master page file which must have screwed up scripting for the drop down controls:

<script language="vbscript" type="text/vbscript" src="somescript.vbs"></script>

Droppingan empty javascript function before the vbscript fixed it andthe drop downs started firing events properly. So if none of the above solutions seem to work, see if you have any vbscript in the header and drop some javascript before it:

<script language="javascript">

function emptyfunc()

hope that helps

Is there any trick to getting a SelectedIndexChanged event to fire on a DropDownlist control in ASP.NET 2008 application?

please help me to solve the problem


Thank in advance.

This worked for me:

I created and and added the list control to its container in the in the container's CreateChildControls method. It seems to be a matter of "when" in the lifecycle that you connect controls that collect user responses...

I have previously used DropDownLists for ASP.NET but now I want to use the same feature for a desktop application. Why is the dropdown list not available to me.

I am using VS2008 and the options that I have are DomainUpDown andListBox !!

I am not sure how to use these features. I want to display the results of a stored procedure in a dropdown list. Can someone please advice me

Kind Regards

Michelle

I had also same problem, when I the AutoPostBack=true then it work nicely, by default it may have EnableViewState=true but not AutopostBack=true. So check ur component what you want to fire with the event.

It seems that this event will only fire if the Value propertychanges....

<asp:dropdownlist id="CategoryDropDown" Runat="server" OnSelectedIndexChanged="CategoryDropDown_SIC" AutoPostBack="True" EnableViewState="True"></asp:dropdownlist></td>

private void Page_Load(object sender, System.EventArgs e)
{
	if(!Page.IsPostBack)
	{
		PopulateDropDown(-1);
	}
}

protected void CategoryDropDown_SIC(object sender, EventArgs e)
{
	category = CategoryDropDown.SelectedIndex;
	PopulateDropDown(category)
}

protected void PopulateDropDown(int category)
{
	SqlConnection conn = null;
	try
	{
		string storeProcedure = ConfigurationManager.GetConfigKey("stp_handoutmaterial_categories");
		string ConnectionString = ConfigurationManager.GetConfigKey("CRM.ConnectionString");
				
		conn = new SqlConnection(ConnectionString);
		conn.Open();

		SqlDataReader reader = GetSqlReader(storeProcedure, conn);
		CategoryDropDown.DataSource = reader;
		CategoryDropDown.DataValueField = "new_category";
		CategoryDropDown.DataTextField = "new_category";
		CategoryDropDown.DataBind();
		if(category != -1)
			CategoryDropDown.SelectedIndex = category;
	}
	catch (SqlException ex)
	{
		string error = ex.ToString();
		ErrorLabel.Text = error;
	}
}

I spent 5 hours trying to get this problem fixed. Dropdownlist's onselectedindexchanged wouldn't fire at all, nor ImageButton's OnClick event. However, for odd reason LinkButton's OnClick worked.

Anyway, my solution was ridiculous. It turned out I had three "<form>" tags in the page. One in the Master Page and two in the current page. I took the two from the page, and WALLA it worked!

I hope this saves people from wasting their valuable time.

I also tried all the options mentioned on this page but nothing worked.

The dropdownlist was in the pagertemplate of the gridview, and I disabled the EnableViewState of Gridview and to my surprise it worked!!!

Not sure why is that so...

yogi

I too was experiencing what others have reported - the postback occurs, but the SelectedIndexChanged event is not called.

I think I've found a definitive cause for this and a workaround.

It seems that this event will only fire if the Value propertychanges. A bit of a bummer if you want different items to return the same value. (I got into this because the same timezone is called different things in different parts of the world.)

The"quick and dirty" code fragments below showthe workaround

To load the list (unbound)

N = 0
While dr.Read 'dr is a DataReader
lstTimezones.Value = N.ToString & "|" & dr(0)
... additional code
N = N +1
End While

In the SelectedIndexChanged event:

ValueSplit()As String = Split(lstTimezones.SelectedValue,"|")
TimezoneCode = ValueSplit(1)

Is this an HTML thing or a Microsoft thing? I'd be interested in knowing.

void Page_Load(object sender, EventArgs e)

{

if (IsPostBack)

{

// This is the line I had to add to get it to work
ddlColours.SelectedIndexChanged +=

new EventHandler(ddlColours_SelectedIndexChanged);

}

else