HttpServerUtility.Transfer Method (IHttpHandler, Boolean)
Assembly: System.Web (in System.Web.dll)
You can write custom HTTP handlers to process specific, predefined types of HTTP requests in any language that is compliant with the Common Language Specification (CLS). Executable code that is defined in the HTTP handler classes instead of conventional ASP (also known as classic ASP) pages or ASP.NET pages responds to these specific requests. HTTP handlers allow for interacting with the low-level request and response services of a Web server that is running Internet Information Services (IIS), and they provide functionality that is similar to ISAPI extensions but with a simpler programming model.
If you set the preserveForm parameter to true, the target page will be able to access the view state of the previous page by using the PreviousPage property.
For security purposes, you should keep the enableViewStateMac attribute set to true. ASP.NET does not verify that the current user is authorized to view the resource delivered by the Transfer method. Although the ASP.NET authorization and authentication logic runs before the original resource handler is called, ASP.NET directly calls the handler indicated by the Transfer method, and does not rerun authentication and authorization logic for the new resource. If the security policy for your application requires clients to have appropriate authorization to access the resource, the application should force reauthorization or provide a custom access-control mechanism.
You can force reauthorization by using the Redirect method instead of the Transfer method. The Redirect method performs a client-side redirect in which the browser requests the new resource. Because this redirect is a new request entering the system, it is subjected to all the authentication and authorization logic of both the IIS and ASP.NET security policy.