Script controls may not be registered after PreRender

[Ben Brooks]

Hello Telerik Team,

I am coming across the following error (Script controls may not be registered after PreRender) when I am trying to create a new tab to load the previous tab User controls into it.
When I call the Addtab() method, it loads the tab but on PageView created after loading all the child controls, I get this following error.
I am using xmlDom to load all UserControls.
Each Tab has a parent UserControl into which I am loading multiple child Controls.

After Iterating through the xmlnodelist, I finally say:
e.PageView.FindControl(parent).FindControl(LeftZone).controls.add(customControl)
Where
parent is the MainParent.ascx, LeftZone is the placeholder into which I need to add teh CustomControl (child.ascx)
When I get into this step, it executes child.ascx perfectly and when i comes out and tries to stepout of this step, I get this error.
I have followed few ref, which include: this and this and this.
Any help regading this issue will be greatly appreciated.

Thanks

[T. Tsonev]

Hi Ben,

As the error suggests, MS Ajax controls ("script controls") can be added to the control tree only before the PreRender stage of the page life-cycle.

It should be possible to change your code to instantiate and place the controls in the Controls collection earlier. The OnLoad event (Page_Load) is the most suitable, but earlier stages will also work - OnInit for example.

I hope this helps.

Greetings,
Tsvetomir Tsonev
the Telerik team