Moving items between listboxes in ASP.net/PHP example

June 12, 2008 by JavaScript   PHP   ASP.NET   Visual Basic  

Ever wanted to move items between two listboxes in ASP.net (or PHP for that matter)?



Someone wanted the exact same thing on codeproject.com a while ago but I didn't give much thought to it, until someone at work asked me how to do it - since he wasn't able to find a viable solution on the internet.

The solution I scripted wasn't as simple as I thought, nor would have liked it to be, my feeling was that one would be able to alter the two listboxes easily using javascript and simply "harvest" the changes (from the Request variables) when its submitted to the server.

The reality however is that only items selected(or highlighted) in the listboxes, will be returned to the server, not the state of the listboxes - so we need to somehow send the state of the listboxes along with the page request.

What I did was, I wrote a javascript script, that serialized the contents of the listboxes as xml to a hiddenfield on the page - whenever you submit the form to the server, a xml string containing the state of the listboxes get sent along - which one can easily process server side (which I will show you just in a while).

function move(fromID, toID, containerID)
{
    var from = document.getElementById(fromID);
    var to = document.getElementById(toID);

    for (var i = 0; i < from.options.length; i++)
    {
        if (from.options[i].selected)
        {					
            to.options.add(new Option(from.options[i].text,from.options[i].value))
            from.remove(i--);
        }
    }

    var container = document.getElementById(containerID);	
    container.value = escape("<listboxes>" + serialize(from) + serialize(to) + "</listboxes>");
}

function serialize(dropdown)
{	
    var value = '<' + dropdown.id + '>';	
    for (var i = 0; i < dropdown.options.length; i++)
    {
        value+= '<option><key><![CDATA[' + encodeURIComponent(dropdown.options[i].text) + ']]></key><value><![CDATA[' + encodeURIComponent(dropdown.options[i].value) + ']]></value></option>';
    }
    value+='</' + dropdown.id + '>';
    return value
}

function unselect(listbox)
{
    document.getElementById(listbox).selectedIndex=-1;
}


Tying it all together (javascript with some .net code), you can easily write yourself an usercontrol, like I did in my example, or create a composite control.

The .net code below is pretty straighforward, you'll noticed two publicly exposed ListBox properties (lstFrom, lstTo), giving us easy access to the listboxes.

If you really need to, you can easily add third, forth listboxes (with slight changes to the javascript code)

The PHP code is quite a bit more involved, I had to create a few classes that give similiar control of what you would expect from an ASP.NET server side control. There is a lot easier ways to do this, but I believe this is a fairly manageable approach.

using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Xml;

public partial class ListPicker : System.Web.UI.UserControl
{
    private XmlDocument _xmlDocument = new XmlDocument();

    public ListBox fromListBox
    {
        get
        {
            return lstFrom;
        }
    }

    public ListBox toListBox
    {
        get
        {
            return lstTo;
        }
    }

    private void PopulateListBox(ListBox listBox)
    {
        listBox.Items.Clear();
        XmlNodeList nodes = _xmlDocument.SelectNodes("listboxes/" + listBox.ClientID + "/option");
        foreach (XmlNode node in nodes)
        {
            listBox.Items.Add(new ListItem(HttpUtility.UrlDecode(node["key"].InnerText), HttpUtility.UrlDecode(node["value"].InnerText)));
        }
    }

    private void PopulateListBoxes()
    {        
        _xmlDocument.LoadXml(HttpUtility.UrlDecode(hdnDropdowns.Value));
        PopulateListBox(lstFrom);
        PopulateListBox(lstTo);
    }

    protected void Page_Load(object sender, EventArgs e)
    {
        Page.ClientScript.RegisterClientScriptInclude("listboxjs", Page.ResolveClientUrl("~/js/listbox.js"));
        if (!IsPostBack)
        {
            String movejs = "move('{0}','{1}','{2}')";
            String unselectjs = "unselect('{0}')";
            lstFrom.Attributes["onclick"] = String.Format(unselectjs, lstTo.ClientID);
            lstTo.Attributes["onclick"] = String.Format(unselectjs, lstFrom.ClientID);
            btnTo.Attributes["onclick"] = String.Format(movejs, lstFrom.ClientID, lstTo.ClientID, hdnDropdowns.ClientID);
            btnFrom.Attributes["onclick"] = String.Format(movejs, lstTo.ClientID, lstFrom.ClientID, hdnDropdowns.ClientID);
        }
        else
        {
            if (!(String.IsNullOrEmpty(hdnDropdowns.Value)))
            {
                PopulateListBoxes();
            }
        }
    }
}
Imports System.Xml

Partial Class ListPicker
    Inherits System.Web.UI.UserControl

    Private _xmlDocument As New XmlDocument()

    Public ReadOnly Property fromListBox() As ListBox
        Get
            Return lstFrom
        End Get
    End Property

    Public ReadOnly Property toListBox() As ListBox
        Get
            Return lstTo
        End Get
    End Property

    Private Sub PopulateListBox(ByVal lstBox As ListBox)
        lstBox.Items.Clear()
        Dim nodes As XmlNodeList = _xmlDocument.SelectNodes("listboxes/" + lstBox.ClientID + "/option")
        For Each node As XmlNode In nodes
            lstBox.Items.Add(New ListItem(HttpUtility.UrlDecode(node.Item("key").InnerText), HttpUtility.UrlDecode(node.Item("value").InnerText)))
        Next
    End Sub

    Private Sub PopulateListBoxes()
        _xmlDocument.LoadXml(HttpUtility.UrlDecode(hdnDropdowns.Value))
        PopulateListBox(lstFrom)
        PopulateListBox(lstTo)
    End Sub

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

Page.ClientScript.RegisterClientScriptInclude("listboxjs", Page.ResolveClientUrl("~/js/listbox.js"))

        If Not IsPostBack Then
            Dim movejs As String = "move('{0}','{1}','{2}')"
            Dim unselectjs As String = "unselect('{0}')"

            lstFrom.Attributes("onclick") = String.Format(unselectjs, lstTo.ClientID)
            lstTo.Attributes("onclick") = String.Format(unselectjs, lstFrom.ClientID)
            btnTo.Attributes("onclick") = String.Format(movejs, lstFrom.ClientID, lstTo.ClientID, hdnDropdowns.ClientID)
            btnFrom.Attributes("onclick") = String.Format(movejs, lstTo.ClientID, lstFrom.ClientID, hdnDropdowns.ClientID)
        Else
            If Not String.IsNullOrEmpty(hdnDropdowns.Value) Then
                PopulateListBoxes()
            End If
        End If
    End Sub
End Class
<?php

require_once("controls.php");
require_once("listbox.php");

class listpicker extends controls
{
    var $lstFrom;
    var $lstTo;
    var $deserializable;

    function listpicker($id)
    {
        $this->attributes['id'] = $id;
        $this->lstFrom = new listbox($id.'_lstFrom');
        $this->lstFrom->attributes['style'] = 'width:200px';
        $this->lstFrom->attributes['onclick'] = "unselect('".$id."_lstTo')";	
        $this->lstTo = new listbox($id.'_lstTo');
        $this->lstTo->attributes['style'] = 'width:200px';
        $this->lstTo->attributes['onclick'] = "unselect('".$id."_lstFrom')";

        if ($_REQUEST[$id.'$hdnDropdowns'])
        {
            $this->deserializable = true;
            $this->xml(urldecode($_REQUEST[$id.'$hdnDropdowns']));			
        }	
    }

    function render()
    {	
    $id = $this->attributes['id'];
    $html='<table>
                <tr>
                    <td>'
                        .$this->lstFrom->render().
                    '</td>
                    <td>
                        <input id="btnTo" type="button" value=">>" onclick="move(\''.$id.'_lstFrom\',\''.$id.'_lstTo\',\''.$id.'_hdnDropdowns\')" />
                            <br />
                        <input id="btnFrom" type="button" value="<<" onclick="move(\''.$id.'_lstTo\',\''.$id.'_lstFrom\',\''.$id.'_hdnDropdowns\')" />
                    </td>
                    <td>'		
                        .$this->lstTo->render().
                    '</td>
                </tr>
            </table>
	        <input type="hidden" ID="'.$id.'_hdnDropdowns" name="'.$id.'$hdnDropdowns" />';		
    return $html;
    }

    function xml($text) 
    {		
        $id = $this->attributes['id'];
        $parser = xml_parser_create();
        xml_parse_into_struct($parser, $text, $vals);
        xml_parser_free($parser);
        $tag = "";

        for($i = 0; $i < count($vals); $i++)
        {	
            switch($vals[$i]['tag'])
            {
                case strtoupper($id.'_lstFrom') : $tag = "lstFrom";	break;
                case strtoupper($id.'_lstTo') : $tag = "lstTo";	break;
            }

            if (($tag) && ($vals[$i]['tag'] == "KEY"))
            {
                $this->{$tag}->addItem($vals[$i]['value'], $vals[$i+1]['value']);					
            }
        }
    }
}

?>


Leave a Comment


Thanks August 19, 2009 by Madhu Gautam

The code was really helpful and I could skip writing this functionality. Thanks - Madhu G

Error April 10, 2009 by Bhargav

Please help! Invalid Callback or post back error

XML already parsed December 19, 2008 by Christoff Truter

Hi Ken Sorry I've only noticed your comment just now. You wont need to deserialize the xml content yourself, the class already takes care of it, you'll notice two properties, lstFrom and lstTo they contain the items (plus updated items from the post request already deserialized for you) If you post to another form, you simply need to instantiate the class on the page (with the same id) eg. $picker = new listpicker("picker"); And simply iterate through the items. eg foreach($picker->lstFrom as $key=>$value) { } foreach($picker->lstTo as $key=>$value) { } Let me know if you've got any questions?

XML ignorant December 16, 2008 by ken

Hi, Matt- I've downloaded you code and tried it and I can see where it works, but I'm stuck when it comes to the XML output. I'm working in PHP, and although I know it's terribly 20th Century of me, I've never used any XML, and when I look at the dozens of XML functions in the PHP manual I don't know where to start. In my application, I'll have a table of items with a serial number, a human-readable name and a status code (active=1, inactive=0). I can see from your sample how to load the listboxes. I want the operator to be able to move objects from the active to the inactive side and vise versa, and get back a set of arrays containing the serial numbers of the now active and inactive items so I can update the database. I'm sure I can derive this info somehow from the XML string you are returning into $_POST, but I'm having trouble getting this. If you could suggest one or two functions which are going to put me on the right road here, I'd appreciate it.

demo works August 19, 2008 by Chris

Hi Klaus, just remove the / from the link to the javascript. It is not loaded. Page.ClientScript.RegisterClientScriptInclude("listboxjs", Page.TemplateSourceDirectory + "js/listbox.js"); Cheers, Chris

June 28, 2008 by Christoff Truter

Hey Bas Seems like I made a little mistake in my php demo as well, sigh hahha, change render(); ?> to render(); ?>, helps to sometimes test demo code, I made the adjustment in the code in the download quickly as well (else nothing will display) I am guessing that your error reporting is set to display all errors? Including non defined variables? In this case that Request wont be set since its not been posted yet, hence the not being defined. Adding error_reporting(5); should hide that error, but a more more gracious approach will be to actually test if the Request on line 22 is set: if (isset($_REQUEST[$id.'$hdnDropdowns'])) { if ($_REQUEST[$id.'$hdnDropdowns']) { $this->deserializable = true; $this->xml(urldecode($_REQUEST[$id.'$hdnDropdowns'])); } }

June 28, 2008 by Bas

Hello Christoff, I stumbled upon your script in my quest for a solution for moving items between 2 list boxes. I am using PHP. When unzipped and opening index.php I get an error "Notice: Undefined index: picker$hdnDropdowns in /usr/local/nagios/share/admin/t/listpicker/php/includes/listpicker.php on line 22". Any ideas as to what this might be? Tia

ResolveClientUrl June 27, 2008 by Christoff Truter

Hi there Klaus Thank you for pointing that out to me. The issue is due to the fact that the code assumes (oeps my fault), that the javascript include resolves to the root of the site (thanks to the ResolveClientUrl function) So it cant find the javascript responsible for doing the work. A quick solution would be to simply change the path accordingly ~/csharp/js/listbox.js, or adding it the javascript includes to the page calling it. A better solution would be to resolve it automatically via some code, like the following for example: Page.ClientScript.RegisterClientScriptInclude("listboxjs", Page.TemplateSourceDirectory + "/js/listbox.js"); I updated the code to reflect this, thank you for letting me know :)

June 26, 2008 by Klaus

I downloaded the demo and it did not work. Kept getting an error in IE... Line: 28 Char: 1 Error: Object Expected Code: 0 URL: http://localhost/listpicker/csharp/default.aspx



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