Redirection in Update Panel Problem

ASP.NET Ajax, Update Panels and Response.Redirect

If your Response.Redirect doesn’t work under UpdatePanel’s callback, then you definitely missing ScriptModule in the web.config:

<httpModules>

<add name="ScriptModule" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>

</httpModules>
The ScriptModule is necessary to provide 3 features needed by the MS AJAX:

• To allow page redirection in a partial page update.
• To be able to call page methods instead of web service methods.
• To serve some files to the users skipping the standard authorization mechanism.

The ScriptModule handles three HttpApplication events:

• PreSendRequestHeaders
• PostAcquireRequestState
• AuthenticateRequest
As i discribe in last post.

The PreSendRequestHeaders event is raised before the server sends the headers to the browser, and it is the last chance to modify them. The ScriptModule handles this event, and checks if the current response code is 302, emitted when you call to the Response.Redirect method.

The ScriptModule fixes redirection problem, because when a redirect is found for a partial page update request, it clears the response (headers and content), maintaining the cookie collection and returning a string as the content of the response. The content of the response is obtained by calling the EncodeString method of an internal class called PageRequestManager.

One thing to point is that the ScriptModule checks if a rest call has generated a redirect, throwing and exception in that case. This is done for security reasons.

The PostAcquireRequestState event is raised after the session data has been obtained. If the request is for a class that implements System.Web.UI.Page and it is a rest method call, the WebServiceData class (that was explained in a previous post) is used to call the requested method from the Page. After the method has been called, the CompleteRequest method is called, bypassing all pipeline events and executing the EndRequest method. This allows MS AJAX to be able to call a method on a page instead of having to create a web service to call a method.

The AuthenticateRequest event is raised after the identity of the current user has been established. The handler for this event sets the SkipAuthorization property of the HttpContext for the current request. This property is checked in the authorization module to see if it has to omit authorization checking for the requested url. Usually an HttpModule use this property to allow anonymous access to some resources (for example, the Login Page if we’re using forms authentication). In our scenario, the ScriptModule sets the SkipAuthorization to true if the requested url is scriptresource.axd or if the authorization module is enabled and the request is a rest request to the authorization web service.