Beginning ASP.NET 4.5 in CSharp and VB Opsylum

Programmatic Redirection x 279
How It Works
When you use Response.Redirect, ASP.NET sends an instruction to the browser to tell it to fetch
a new page. In technical terms, it sends a “302” HTTP status code to indicate the page has moved
temporarily. With this instruction it also sends the new URL, so the browser understands what page
to fetch next. In this exercise, the new page was Target.aspx?Test=SomeValue, which contains
both the page name and a query string. The Target.aspx page is then requested by the browser, the
Page_Load event fires, and the query string is displayed on the label in the page. Because of this client
redirect, the new page name and query string are fully exposed to the client. If you use Response
.RedirectPermanent, ASP.NET sends out a “301 Moved Permanently” instruction. For some browsers,
this means that if the original page has previously been cached by the browser, you’re taken automatically
to the new page if you request the original page. Once the browser cache is cleared, a request is
made again for the original page. Other browsers may continue to request the original page. Search
engines interpret the 301 redirect as “don’t bother fetching this page again” and the page will no longer
be indexed.
Redirects follow the same naming scheme for URLs as those used in server controls, so you can redirect
to a page like ~/Default.aspx to redirect the user to the file Default.aspx in the website’s root.
In contrast to Response.Redirect and Response.RedirectPermanent, there is also Server
.Transfer, which redirects to another page at the server.
Server-Side Redirects
Server-side redirects are great if you want to send out a different page without modifying the client’s
address bar. This enables you to hide details of page names and query strings, which may lead to
cleaner URLs from a user’s point of view. This is often used in so-called URL-rewrite scenarios that
are used to create pretty URLs. For example, a user may request a page like this:
http://www.domain.com/Cars/Volvo/850/T5/
Under the hood the server might transfer to:
http://www.domain.com/Cars/ShowCar.aspx?Make=643&Model=984&Type=7345
Clearly, the first URL is a lot easier to understand and type in a browser. It also enables a user to
guess other URLs that match the same pattern. For example, there’s a fair chance you can request a
page like this:
http://www.domain.com/Cars/Volvo/V70/R/
and end up with the right page showing you the Volvo V70 R.
In addition to being easier to understand, server-side transfers may also speed up your site a little.
Instead of sending a response to the browser to tell it to fetch a new page, which results in a new
request for a page, you can transfer the user directly to a new page, saving you some network
overhead.
Server-side transfers are carried out with the Server object. Just as the Request and Response
objects you saw earlier give you information about the request and the response, so does the Server