Accessing values in codebehind created with JavaScript

#1
wim DC

Posted 28 April 2010 - 11:19 AM

Writes binary right handed and hex left handed

Members
2,083 posts

Programming Language:Java, JavaScript, PL/SQL
Learning:Java

So, here's the thing.
on my .aspx page i have 2 divs. In div 1 i have 4 other divs (could be labels to, or somethign else ).
With JavaScript i then let the user drag (using help from JQuery ^^) the new divs from div1 to div2 and back.

Now, when i click a button I should know which div IDs are in div2(or which are not in div1)

To make it myself a bit easier to know which div is placed where (as divs aren't runat=server), i made an invisble ListBox(runat="server") where i keep copies of the divIDs that get dragged in div2.
Problem is that by the time it reaches the btn_click code in code-behind, the page has refreshed and thus the listbox is empty again, and there's nothing to get from there.

So somehow i must send the stuff from the listbox to the server-side BEFORE the page is refreshed and the listbox is clear... and i don't know how :crying:

My only requirement, and problem is that i do not want any postbacks untill the button is pressed.

Any ideas?

#2
gokuajmes

Posted 28 April 2010 - 10:42 PM

Programming God

Members
518 posts

well you could do this using a Hidden Field with ViewState enabled. i had a similar issue some day this solved mine!!
below code works for me

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Default Page</title>
    <link rel="stylesheet" type="text/css" href="StyleSheet.css" />

    <script type="text/javascript" src="jquery-1.4.2.js"></script>

    <script type="text/javascript" src="jquery-ui.min.js">
    
    </script>

</head>
<body>
    <form id="form1" runat="server">
        <div>
            <asp:ScriptManager ID="ScriptManager1" runat="server">
            </asp:ScriptManager>
            <asp:UpdatePanel ID="UpdatePanel1" runat="server">
                <ContentTemplate>
                    <style type="text/css">
    #draggable { width: 150px; height: 150px; padding: 0.5em; }
    </style>

                    <script type="text/javascript">
                    function drag(){
    $("#draggable").draggable();
    document.getElementById("hd1").value = "Div dragged";
    }
                    </script>

                    <div class="demo">
                        <div id="draggable" style="background-color:Gray" onclick="drag()">
                            <p>
                                Drag me around</p>
                        </div>
                        <asp:HiddenField ID="hd1" runat="server" />
                        <asp:Button ID="btnpost" runat="server" Text="PostBack" OnClick="btnpost_Click" />
                        <asp:Label ID="Label1" runat="server"></asp:Label>
                </ContentTemplate>
            </asp:UpdatePanel>
        </div>
    </form>
</body>
</html>

also in the Code Behind write this code

protected void btnpost_Click(object sender, EventArgs e)
    {
        if (hd1.Value == "")
        {
            Label1.Text = "you did not drag anything";
        }
        Label1.Text = "you dragged "+hd1.Value;
    }

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#3
wim DC

Posted 29 April 2010 - 09:14 AM

Writes binary right handed and hex left handed

Members
2,083 posts

Programming Language:Java, JavaScript, PL/SQL
Learning:Java

Thank you very much! Last night, while i was trying to fall asleep, i came up with the idea that textboxes don't loose their text on postbacks, so instead of storing stuff in the listbox i may store IDs in the textbox.
So i was allready thinking of making an invisible textbox. A hidden field is basicly the same but probably more secure i suppose^^.

Been looking for a solution for the ListBox for hours...turns out that the main problem with the ListBox was that it's impossible to do a databind from JavaScript... Which makes sence in some way.

#4
gokuajmes

Posted 30 April 2010 - 12:56 AM

Programming God

Members
518 posts

you are welcome :)

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