Extender control 'cpe_1' cannot extend 'pB_1'. Extender controls of type 'AjaxControlToolkit.CollapsiblePanelExtender' cannot extend controls of type 'Panel'.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.InvalidOperationException: Extender control 'cpe_1' cannot extend 'pB_1'. Extender controls of type 'AjaxControlToolkit.CollapsiblePanelExtender' cannot extend controls of type 'Panel'.

Source Error: 

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace: 


[InvalidOperationException: Extender control 'cpe_1' cannot extend 'pB_1'. Extender controls of type 'AjaxControlToolkit.CollapsiblePanelExtender' cannot extend controls of type 'Panel'.]
   System.Web.UI.ScriptControlManager.VerifyTargetControlType(TExtenderControl extenderControl, Control targetControl) +441617
   System.Web.UI.ScriptControlManager.RegisterExtenderControl(TExtenderControl extenderControl, Control targetControl) +75
   System.Web.UI.ScriptManager.RegisterExtenderControl(TExtenderControl extenderControl, Control targetControl) +95
   System.Web.UI.ExtenderControl.RegisterWithScriptManager() +176
   AjaxControlToolkit.ExtenderControlBase.OnPreRender(EventArgs e) +19
   System.Web.UI.Control.PreRenderRecursiveInternal() +103
   System.Web.UI.Control.PreRenderRecursiveInternal() +175
   System.Web.UI.Control.PreRenderRecursiveInternal() +175
   System.Web.UI.Control.PreRenderRecursiveInternal() +175
   System.Web.UI.Control.PreRenderRecursiveInternal() +175
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2496