Had a go to meeting to discuss Telerik tools integration with Desislava Nikolo and another consultant. They acknowledged this issue and resolved to contact me after the meeting to provide a fix. 
Basically, from the Telerik Tab in the IDE 2010, I am unable to load any of the RAD tools for development.

I have a RadGrid with several thousand elements on it. In attempting to improve performance, the Visual Studio profiler informed me that it spent more than half of the request in PopulatePlainPanels checking whether something was in a list. (see attached before.png)

I changed the type of the variable plainPanelsClientIDs in RadAjaxControl.cs to be a HashSet<string> instead of a List<string>. As a knock-on effect, I had to import System.Linq into RadAjaxManager.cs to get the .toArray() call to work.

The result in the attached after.png shows the percentage of execution time dropped from 55% to 3%.

I'd appreciate it if the team would evaluate this change for inclusion in future releases.

Note 1: I have not done extensive testing on this, so I don't know what might break. The variable isn't referenced much, so the only thing I'm suspicious of is reflection, which I didn't check for and don't expect.
Note 2: If importing Linq is undesirable, a more manual conversion to an array can be done pretty easily.
Note 3: plainPanelsClientIDs is .add() 'ed to in two places, and both check for membership before being called. This shouldn't be necessary for a HashSet, which simply doesn't add if it's there. This seems a very minor improvement, but I didn't actually try it yet.

Attached is a reproduction project page with a <script> containing a workaround.

Reproduction steps:

1) Run the page

2) Hover quickly between the two colored squares (do this up to 15-20 seconds)

3) Observe the error in the browser's console:

Uncaught RangeError: Maximum call stack size exceeded
    at Function.Array.addRange 
    at Telerik.Web.UI.RadAjaxManager._executePendingRequest 
    at Object._endRequest 
    at Array.<anonymous> 
    at Sys.WebForms.PageRequestManager._endPostBack 
    at Sys.WebForms.PageRequestManager._scriptsLoadComplete 
    at Sys.WebForms.PageRequestManager.<anonymous>   
    at Sys._ScriptLoader._loadScriptsInternal 

Workaround: Place/load this script somewhere after the ScriptManager of the page

<script>
    Telerik.Web.UI.RadAjaxControl.prototype._executePendingRequest = function () {
        var pendingRequest = Array.dequeue(this._requestQueue);

        var eventTarget = pendingRequest[0];
        var eventArgument = pendingRequest[1];

        if (this._requestQueue.length > 0 && this.__id != "") {
            var currentAjaxControl = $find(this.__id);
            if (currentAjaxControl) {
                Array.addRange(currentAjaxControl._requestQueue, this._requestQueue);
                // optional, uncomment if issue persists
                //if (currentAjaxControl._requestQueue.length > currentAjaxControl._requestQueueSize) {
                //    // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/slice#parameters 
                //    // using negative index for start to get the last N elements
                //    currentAjaxControl._requestQueue =
                //        currentAjaxControl._requestQueue.slice(-currentAjaxControl._requestQueueSize)
                //}
            }
        }

        var requestManager = Sys.WebForms.PageRequestManager.getInstance();
        requestManager._doPostBack(eventTarget, eventArgument);
    }
</script>

We have code for our ajaxified submit forms to disable the submit button on request start and re-enabled it on request end. This used to work, but when we upgraded to the latest build (2020.2.617), setting the disabled property to false now throws an error in IE from the WebResource.axd file (does not appear to have a problem in Firefox). The attached demo project shows exactly where the error occurs. Just click the Search button.

Attached picture shows an example of the error message thrown. The error does not appear to be with our javascript code itself; all the variables are populated and valid. It looks like something is getting triggered in the WebResource code when we set the disabled property to false and that is where the break is occurring.

I am using a component (GoogleMapControl) that inherit IExtenderControl . when i add it in to radajaxmanager updated controls or if i use it in dynamically loaded usercontrol by RadTab & RadMultiPage i am getting error of Unable to cast object of type 'GoogleMaps.Markers.GoogleMarkers' to type 'System.Web.UI.ExtenderControl'.

When i check the error detail by AsyncPostBackError event, i found that error comes from Telerik.Web.UI.ProxyScriptControl.GetChildScriptDescriptorsRecursive(Control parent, ArrayList scriptDescriptors).

Someones lived same problem old but same... As in https://dnntracker.atlassian.net/browse/DNN-25819

When AutoResizeHeight is set to true in Chrome, on Editing in the content area, the view jerks, for example, when I select some text and click bold the view moves up. This happens on and off. The requirement for an editor is not to change position of the text which is being edited, it distracts the user.

Hi guy,

      I want use alert function in radajaxmanager,  After i  set  radajaxmanager.alert, if c'ode is running it ,page will pop-up a window. but this window is middle positon in page.
how can i  solve this question.thanks.


David

Hi guy,

      I want use alert function in radajaxmanager,  After i  set  radajaxmanager.alert, if code is running it ,page will pop-up a window. but this window is not middle positon in current page.
How can i  solve this question.thanks.


David

moving application to godaddy web server hosting results in tab control not handling changing tabs.  app is using ajax handler and multpage.  its works on locall iis server.  Also tried calendar control which also did not change date when clicked.  

Using a hidden button and calling its .click() method is sometimes used to invoke a postback under some application logic conditions. If you use the jQuery method and a RadAjaxPanel, this will no longer work with jQuery3 because its strict mode causes the MS AJAX scripts to throw an error.

Below is a sample repro of the scenario and it shows two of the workarounds. The third workaround is to downgrade jQuery to an older version (for example, 1.11.1 which is the previous version the suite used): https://docs.telerik.com/devtools/aspnet-ajax/controls/scriptmanager/disabling-the-embedded-jquery


        <telerik:RadScriptManager ID="RadScriptManager1" runat="server">
            <Scripts>
                <asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.Core.js" />
                <asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.jQuery.js" />
                <asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.jQueryInclude.js" />
            </Scripts>
        </telerik:RadScriptManager>
        <telerik:RadCodeBlock runat="server" ID="rcb1">
            <script>
                function clickHiddenButton1() {
                    $telerik.$("#<%=Button1.ClientID%>").click();
                    //workaround 1
                    //__doPostBack("<%=Button1.UniqueID%>", "");
                    //workaround 2
                    //$find("<%=rap1.ClientID%>").ajaxRequest();
                }
            </script>
        </telerik:RadCodeBlock>
        <asp:Button Text="click hidden button" ID="testButton1" OnClientClick="clickHiddenButton1(); return false;" runat="server" />
        <telerik:RadAjaxPanel runat="server" ID="rap1" OnAjaxRequest="rap1_AjaxRequest">
            <asp:Label Text="" ID="Label1" runat="server" />
            <asp:Button Style="display: none;" Text="hidden button" ID="Button1" OnClick="Button1_Click" runat="server" />
        </telerik:RadAjaxPanel>

A grid in a RadAjaxPanel will fire several requests when exporting if there is a RadAjaxManager on the page as well.

Stems from the _setupExclusionFilters function where each RadAjaxControl adds as a handler to Sys.WebForms.PageRequestManager.getInstance().add_initializeRequest which does a  sender._form.submit(); and gets called in the initialize method of the control.

The resolution is to use only RadAjaxManager to AJAX-enable complex pages that require the built-in exports as well and make sure to remove all RadAjaxPanel instances. This is the better approach anyway: http://docs.telerik.com/devtools/aspnet-ajax/controls/ajaxmanager/troubleshooting/controls-wrapped-in-ajaxpanel-and-added-to-ajaxmanager-settings

Repro and example solutions are added in the file attached below.

The Ajax in the sample page is made using:

$find("<%= RadAjaxManager.GetCurrent(Page).ClientID %>").ajaxRequest();

In on the page the AjaxManger updates the panel, in the other the setting is that the proxy should update the panel. This is invalid setting.

<telerik:AjaxSetting AjaxControlID="RadAjaxManagerProxy1" >
    <UpdatedControls>
        <telerik:AjaxUpdatedControl ControlID="rsLeftPanel" LoadingPanelID="ralp1" />
    </UpdatedControls>
</telerik:AjaxSetting>

The correct way of doing this is to use add the settings programatically, or to use the ajaxRequestWithTarget instead of ajaxRequest method
http://docs.telerik.com/devtools/aspnet-ajax/controls/ajax/radajaxmanager/how-to/add-ajaxsettings-programmatically

Based on feedback received from our customer, we can further improve our TypeScript definitions - the main concern is that there are still missing methods and incorrect signatures.

The RadTextBox are placed inside a asp gridview. When an item from the combo box in the page is selected. The server side logic hide one of the columns of the gridview using such approach:

grdExamples.Columns[2].Visible = false;

This, however, keeps the controls inside the vary same GridView. So during Ajax their ScriptDescriptrs got registered in the ScriptManager. When the result $create execute client side, the JS error is thrown.

It can not be fixed in general, because we can not cover scenarios where the control is:

1. Visible

2. In the control collection. (have .Page!=null)

3. All it's parents are visible.

4. Does not render, because it's parent control ( the gridview) decides not to render some of it's childs.

When all of 1,2,3,4 are true, the control will describe, but not visible in the output HTML resulting in error.

It will happen in all controls (not only RadTextBox), when you are using the RadAjaxManager. Since the manager registers the ScriptDescriptors manually per control, before the Render of the page, therefore it can't know if the control is "Really Visible". This is limitation of the manager, that can not be changed without breaking fundamentals of how it works.

The Response.Redirect is not supposed to work during through Ajax call.