Telerik UI for ASP.NET AJAX


When using RadScriptManager with EnableScriptCombine=True the controls stop working as you get a JavaScript error.

Cause: There are different reasons for this error to happen. Please, check the list below: 1) RadScriptManager was unable to correctly determine if the browser supports gzip/deflate compression; 2) A custom ScriptReference is added to RadScriptManager (having a Path property specified), which depends on the combined scripts or vice-versa; 3) There is an unfound bug in RadScriptManager;

Resolution: Below are the respective resolutions for the problems, described above: 1) Implement your own browser detection mechanism and use the OutputCompression property of RadScriptManager to control it. You might also try to reinstall the browser, or restore its initial settings; 2) Upgrade to the latest Telerik.Web.UI version. You can download it from your ClientNet account. RadScriptManager now supports the addition/insertion of custom scripts depending/dependent on other scripts. The custom script is added as a separate <script> tag and the general merged script is split respectively. 3) Check the Release notes - the problem might have already been fixed. Upgrade to the latest Telerik.Web.UI version and check if the bug is not fixed while fixing another one. Send us a small website, demonstrating the problem.


You receive the following error even if you had already added the handler.

~/Telerik.Web.UI.WebResource.axd' is missing in web.config. RadScriptManager requires a HttpHandler registration in web.config.


The <handlers> or <httpHandlers> sections are placed under the <location> section and RadScriptManager cannot find them.


Set the EnableHandlerDetection="false" property of RadScriptManager.


There is not RadScriptManagerProxy, what should I do?


You can use the ScriptManagerProxy. Yes, place the RadScriptManager control on the page /master page and the ScriptManagerControl on the user control / content page.


The RadScriptManager is incompatible with the Ajax Control Toolkit (Version number 40412 and higher).

NOTE: Since the winter of 2013, the AjaxControlToolkit is incompatible with the standard asp:ScriptManager and, thus, by extension, with telerik:RadScriptManager. This means that using the ToolkitScriptManager can break the Telerik controls and a potential workaround is setting its CombineScript property to false. Moreover, we cannot guarantee that the controls from the AjaxControlToolkit suite will work when RadScriptManager is used.

For older version of the AjaxControlToolkit, there are specific errors and resolutions that you can find below.

The following error appears when controls from the ACT are present on the page:

Microsoft JScript runtime error: AjaxControlToolkit requires ASP.NET Ajax 4.0 scripts. Ensure the correct version of the scripts are referenced. If you are using an ASP.NET ScriptManager, switch to the ToolkitScriptManager in AjaxControlToolkit.dll.


Resolution for .NET 4.0 projects:

Upgrade the RadControls for ASP.NET AJAX version 2010.1.625 or newer.

Important: Make sure you use the .NET 4.0 build of both Telerik.Web.UI.dll and AjaxControlToolkit.dll

If upgrade is not option you can use the following workaround:

<telerik:RadScriptManager runat="server" EnableScriptCombine="false" />

Resolution for .NET 3.5 projects:

Override the references to MicrosoftAjax.js and MicrosoftAjaxWebForms.js to point to the ACT script files.

<telerik:RadScriptManager runat="server">
       <asp:ScriptReference Assembly="System.Web.Extensions, Version=, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
           Name="MicrosoftAjax.js" Path="Scripts-40412/MicrosoftAjax.js" />
       <asp:ScriptReference Assembly="System.Web.Extensions, Version=, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
           Name="MicrosoftAjaxWebForms.js" Path="Scripts-40412/MicrosoftAjaxWebForms.js" />

The script files are obtained by building the ACT from source. Sample project, including the scripts for version 40412, is attached.


Using RadControls with RadScriptManager on your login page throws one of the following errors:

ASP.NET Ajax client-side framework failed to load

'Sys' is undefined

'Telerik.Web.UI' is undefined


As the website denies access to all pages to unauthorized users, access to the Telerik.Web.UI.WebResource.axd handler is unauthorized. This causes the handler to serve the content of the login page instead of the combined scripts, hence the error.


Add a <location> section to the application configuration file to allow access to Telerik.Web.UI.WebResource.axd to all users, like:

<location path="Telerik.Web.UI.WebResource.axd">
       <allow users="*"/>


Getting 'Sys' is undefined error caused by 404 error in the WebResource.axd file when there are multiple handlers that contain *.axd in their path attribute (for example: ASPNET-ISAPI-1.1-AXD).


The issue is observed because all such handler must be placed at the end of the web.config otherwise they are going to intercept all requests for other .axd handlers. That is why in order to solve the problem one should structure the web.config in a way that the specialized handlers, such as Telerik.Web.UI.WebResource.axd , are placed in the beginning of the web.config whereas the more generic ones, which accept path with *.axd are placed at the end.

Current limitation:

Gettng [NullReferenceException: Object not set to an instance of an object.] error when using RadScriptManager and loading scripts from assemlies with short names while with there is no error with a standard ScriptManager.


The issue is observed because the standard ScriptManager automatically resolves the short name whereas RadScriptManager require full name. We will optimize that behavior in the future, however until then please make use of the fully qualified name as below.

<asp:ScriptReference Name="WebForms.js" Assembly=" System.Web, Version=, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
<asp:ScriptReference Name="WebUIValidation.js" Assembly=" System.Web, Version=, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"" /