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Version Q2 2011 released 07/12/2011
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Ajax / Persisting JavaScript







  • RadAjax controls re-initialize JavaScript code after an AJAX request has been performed. This behavior is very important when working with third party controls inside the RadAjaxPanel that use rich JavaScript functionality.

    The example contains a JavaScript code block within the RadAjaxPanel that is evaluated on page load. The code holds some logic for browsing through a web galery of images. When an AJAX request is performed, the RadAjaxPanel re-initializes the JavaScript code and as a result the custom functionality works properly.

Source Code

C# VB.NET
Show code in new window Demo isolation steps
  • <%@ Page Language="vb" CodeFile="DefaultVB.aspx.vb" Inherits="Telerik.AJAXExamplesVBNET.AJAX.Examples.Common.PersistJavaScript.DefaultVB" %>

    <%@ Register TagPrefix="telerik" Namespace="Telerik.Web.UI" Assembly="Telerik.Web.UI" %>
    <%@ Register TagPrefix="telerik" TagName="Footer" Src="~/Common/Footer.ascx" %>
    <%@ Register TagPrefix="telerik" TagName="HeadTag" Src="~/Common/HeadTag.ascx" %>
    <%@ Register TagPrefix="telerik" TagName="Header" Src="~/Common/Header.ascx" %>
    <!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">
        <telerik:HeadTag runat="server" ID="Headtag1"></telerik:HeadTag>
        <!-- custom head section -->
        <!-- end of custom head section -->
    </head>
    <body class="BODY">
        <form runat="server">
        <telerik:Header runat="server" ID="Header1" NavigationLanguage="VB"></telerik:Header>
        <!-- content start -->
        <telerik:RadScriptManager ID="RadScriptManager1" runat="server">
        </telerik:RadScriptManager>
        <div class="module" style="width: 350px; margin-right: 20px;">
            <telerik:RadAjaxPanel ID="RadAjaxPanel1" ClientEvents-OnResponseEnd="CreateScripts"
                runat="server" LoadingPanelID="LoadingPanel1">
    <asp:Button ID="Button1" OnClick="Button1_Click" runat="server" Text="Start ajax request"
    CssClass="qsfButtonBigger"></asp:Button>
                <br />
                <br />
                <br />
                <div id="Container" style="width: 350px; height: 244px;">
                </div>
                <br />
                <br />

                <script type="text/javascript">
                            /*<![CDATA[*/
                            function CreateScripts()
                            {
                                window.currentIndex = 0;
            
                                var MyImageCollection = new Array("img/img_1.jpg", "img/img_2.jpg", "img/img_3.jpg");
                                var MyImage = new Image();
                                MyImage.id = "myImg";
                                MyImage.src = "img/img_1.jpg";
                                MyImage.setAttribute('galleryimg', 'no');
        
                                var ControlsContainer = document.getElementById("Container");
        
                                function UpdateImage()
                                {
                                    NextButton.disabled = (window.currentIndex > MyImageCollection.length - 2)? true : false;
                                    PreviousButton.disabled = (window.currentIndex < 1)? true : false;
                                    MyImage.src = MyImageCollection[window.currentIndex];
                                }
        
                                var PreviousButton = document.createElement("button");
                                PreviousButton.innerHTML = "&laquo;&nbsp;previous";
                                PreviousButton.className = "qsfButton";
                                PreviousButton.style.marginBottom = 14 + "px";
                                PreviousButton.disabled = true;
                                PreviousButton.setAttribute('type','button');
                                PreviousButton.onclick = function(e)
                                {
                                    if(!e)
                                        var e = window.event;
                                    
                                    if(e.preventDefault)
                                    {
                                        e.preventDefault();
                                    }
                                    
                                    window.currentIndex--;
                                    UpdateImage();
                                };
        
                                var NextButton = document.createElement("button");
                                NextButton.innerHTML = "next&nbsp;&raquo;";
                                NextButton.className = "qsfButton";
                                NextButton.style.marginLeft = 14 + "px";
                                NextButton.style.marginBottom = 14 + "px";
                                NextButton.disabled = false;
                                NextButton.setAttribute('type','button');
                                NextButton.onclick = function(e)
                                {
                                    if(!e)
                                        var e = window.event;
        
                                    if(e.preventDefault)
                                    {
                                        e.preventDefault();
                                    }
        
                                    window.currentIndex++;
                                    UpdateImage();
                                };
        
                                ControlsContainer.appendChild(PreviousButton);
                                ControlsContainer.appendChild(NextButton);
                                ControlsContainer.appendChild(document.createElement("br"));
                                ControlsContainer.appendChild(MyImage);
                         };
                        
                         CreateScripts();
                            /*]]>*/
                </script>

            </telerik:RadAjaxPanel>
            <telerik:RadAjaxLoadingPanel ID="LoadingPanel1" runat="server" MinDisplayTime="300" />
        </div>
        <!-- content end -->
        <telerik:Footer runat="server" ID="Footer1"></telerik:Footer>
        </form>
    </body>
    </html>

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