Still celebrating National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17


ASP.Net/C# - How to get value of a regular HTML Select List Box in code behind?

Posted on 2008-06-25
Medium Priority
Last Modified: 2012-08-14
Hello all I could really use some help here.  I have a ASPX page that has a regular select list on it where the user can add and remove items via javascript.  I need to in my code behind on a save loop through each value that was entered into that select list to create a semi-colon seperated string.  Then the same coming back into the page I need to parse through the values and add to the list box.  I know how to handle the for loop for the coming back with a string split.  I just need to know how to add the item to the select list HTML.  Any help would be much appreciated.  Attached is the code from the page.
<script type="text/javascript" language="javascript">
	function remove()
		var list = window.document.getElementById('myList');
		var keepLooking = true;
		while ( keepLooking ) {
			list.remove( list.options.selectedIndex );
			if ( list.options.selectedIndex < 0 ) {
				keepLooking = false;
	function add()
		var list = window.document.getElementById('myList');
		var tbox = document.getElementById('myText');
		var tval = tbox.value;
        var newOpt = document.createElement('option');
        var txt = document.createTextNode(tval);
        newOpt.setAttribute('value', tval);
        //newOpt.text = tval;
        //newOpt.value = tval;
<select id="myList" name="myList" size="10" style="width:200px;"></select>
<a href="javascript:remove();">Remove</a><br />
<input type="text" id="myText" value="" style="width:200px;"/>
<a href="javascript:add();">Add</a>

Open in new window

Question by:sbornstein2
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 3
LVL 21

Accepted Solution

naspinski earned 1000 total points
ID: 21864804
Instead, why don't you make this an asp:dropdownlist and change the javascript to accommodate the newly generated IDs (view source).  Ass the asp controls just make an html drop list anyways, jsut takes care of a lot of the footwork of getting it to the backend.

Author Comment

ID: 21864937
ya that is what I was thinking but im not sure how to do that.  Do I use just the name of the listbox? and also the other problem is I just need to make sure it does not post back.
LVL 21

Expert Comment

ID: 21864975
If it does not postback, there is no way to get the codebehind (c#) the value, as that is server side.

So you need a postback... you could use an ajax asp:updatepanel for an asynch postback.

Also, to get the asp-made ids, just run your page, go into your browser and view source.  Then find the dropdowns and you can see the ID that asp made for them... use those.
Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!


Author Comment

ID: 21865002
ok so ya this would work and then I can use:

StringBuilder sb = new StringBuilder();
            foreach (ListItem item in lstBulletPoints.Items)
                    sb.Append(item.Text.ToString() + ";");
                catch (Exception)
                    // ignore
that will create my list.

Can that ID ever change though and is there a better way to use like a client id or something
LVL 21

Expert Comment

ID: 21865033
The ID will never change.  It is a bit of a pain, but in order to allow both server and client-side scripts to work on the same objects, you have to coax them into working sometimes.
LVL 39

Assisted Solution

by:Pratima Pharande
Pratima Pharande earned 1000 total points
ID: 21865043
<select id="myList" name="myList" size="10" style="width:200px;" runat="server"></select>

To add values thorugh

LVL 21

Expert Comment

ID: 21865074
wow... i feel like an idiot since I didn't even think of making it a server control :P  good call pratima

Just have to make sure it is inside of a form tag that is also runat="server"

Author Closing Comment

ID: 31470523
both were helpful thanks guys.  I might use AJAX and a server control instead but nevertheless thanks for the help and awesome info

Featured Post

New feature and membership benefit!

New feature! Upgrade and increase expert visibility of your issues with Priority Questions.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Introduction This article shows how to use the open source plupload control to upload multiple images. The images are resized on the client side before uploading and the upload is done in chunks. Background I had to provide a way for user…
The article shows the basic steps of integrating an HTML theme template into an ASP.NET MVC project
Monitoring a network: how to monitor network services and why? Michael Kulchisky, MCSE, MCSA, MCP, VTSP, VSP, CCSP outlines the philosophy behind service monitoring and why a handshake validation is critical in network monitoring. Software utilized …
In this video you will find out how to export Office 365 mailboxes using the built in eDiscovery tool. Bear in mind that although this method might be useful in some cases, using PST files as Office 365 backup is troublesome in a long run (more on t…
Suggested Courses

722 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question