Server.Transfer Vs. Response.Redirect

问题:

What is difference between Server.Transfer and Response.Redirect?

• What are advantages and disadvantages of each?
• When is one appropriate over the other?
• When is one not appropriate?

回答1:

Response.Redirect simply sends a message (HTTP 302) down to the browser.

Server.Transfer happens without the browser knowing anything, the browser request a page, but the server returns the content of another.

回答2:

Response.Redirect() will send you to a new page, update the address bar and add it to the Browser History. On your browser you can click back.

Server.Transfer() does not change the address bar. You cannot hit back.

I use Server.Transfer() when I don't want the user to see where I am going. Sometimes on a "loading" type page.

Otherwise I'll always use Response.Redirect().

回答3:

To be Short: Response.Redirect simply tells the browser to visit another page. Server.Transfer helps reduce server requests, keeps the URL the same and, with a little bug-bashing, allows you to transfer the query string and form variables.

Something I found and agree with (source):

Server.Transfer is similar in that it sends the user to another page with a statement such as Server.Transfer("WebForm2.aspx"). However, the statement has a number of distinct advantages and disadvantages.

Firstly, transferring to another page using Server.Transfer conserves server resources. Instead of telling the browser to redirect, it simply changes the "focus" on the Web server and transfers the request. This means you don't get quite as many HTTP requests coming through, which therefore eases the pressure on your Web server and makes your applications run faster.

But watch out: because the "transfer" process can work on only those sites running on the server; you can't use Server.Transfer to send the user to an external site. Only Response.Redirect can do that.

Secondly, Server.Transfer maintains the original URL in the browser. This can really help streamline data entry techniques, although it may make for confusion when debugging.

That's not all: The Server.Transfer method also has a second parameter—"preserveForm". If you set this to True, using a statement such as Server.Transfer("WebForm2.aspx", True), the existing query string and any form variables will still be available to the page you are transferring to.

For example, if your WebForm1.aspx has a TextBox control called TextBox1 and you transferred to WebForm2.aspx with the preserveForm parameter set to True, you'd be able to retrieve the value of the original page TextBox control by referencing Request.Form("TextBox1").

回答4:

Response.Redirect() should be used when:

• we want to redirect the request to some plain HTML pages on our server or to some other web server
• we don't care about causing additional roundtrips to the server on each request
• we do not need to preserve Query String and Form Variables from the original request
• we want our users to be able to see the new redirected URL where he is redirected in his browser (and be able to bookmark it if its necessary)

Server.Transfer() should be used when:

• we want to transfer current page request to another .aspx page on the same server
• we want to preserve server resources and avoid the unnecessary roundtrips to the server
• we want to preserve Query String and Form Variables (optionally)
• we don't need to show the real URL where we redirected the request in the users Web Browser

回答5:

Response.Redirect redirects page to another page after first page arrives to client. So client knows the redirection.

Server.Transfer quits current execution of the page. Client does not know the redirection. It allows you to transfer the query string and form variables.

So it depends to your needs to choose which is better.

回答6:

"response.redirect" and "server.transfer" helps to transfer user from one page to other page while the page is executing. But the way they do this transfer / redirect is very different.

In case you are visual guy and would like see demonstration rather than theory I would suggest to see the below facebook video which explains the difference in a more demonstrative way.

https://www.facebook.com/photo.php?v=762186150488997

The main difference between them is who does the transfer. In "response.redirect" the transfer is done by the browser while in "server.transfer" it’s done by the server. Let us try to understand this statement in a more detail manner.

In "Server.Transfer" following is the sequence of how transfer happens:-

1.User sends a request to an ASP.NET page. In the below figure the request is sent to "WebForm1" and we would like to navigate to "Webform2".

2.Server starts executing "Webform1" and the life cycle of the page starts. But before the complete life cycle of the page is completed “Server.transfer” happens to "WebForm2".

3."Webform2" page object is created, full page life cycle is executed and output HTML response is then sent to the browser.

While in "Response.Redirect" following is the sequence of events for navigation:-

1.Client (browser) sends a request to a page. In the below figure the request is sent to "WebForm1" and we would like to navigate to "Webform2".

2.Life cycle of "Webform1" starts executing. But in between of the life cycle "Response.Redirect" happens.

3.Now rather than server doing a redirect , he sends a HTTP 302 command to the browser. This command tells the browser that he has to initiate a GET request to "Webform2.aspx" page.

4.Browser interprets the 302 command and sends a GET request for "Webform2.aspx".

In other words "Server.Transfer" is executed by the server while "Response.Redirect" is executed by thr browser. "Response.Redirect" needs to two requests to do a redirect of the page.

So when to use "Server.Transfer" and when to use "Response.Redirect" ?

Use "Server.Transfer" when you want to navigate pages which reside on the same server, use "Response.Redirect" when you want to navigate between pages which resides on different server and domain.

Below is a summary table of which chalks out differences and in which scenario to use.

回答7:

The beauty of Server.Transfer is what you can do with it:

TextBox myTxt = (TextBox)this.Page.PreviousPage.FindControl("TextBoxID");

You can get anything from your previous page using the above method as long as you use Server.Transfer but not Response.Redirect

回答8:

In addition to ScarletGarden's comment, you also need to consider the impact of search engines and your redirect. Has this page moved permanently? Temporarily? It makes a difference.

see: Response.Redirect vs. "301 Moved Permanently":

We've all used Response.Redirect at one time or another. It's the quick and easy way to get visitors pointed in the right direction if they somehow end up in the wrong place. But did you know that Response.Redirect sends an HTTP response status code of "302 Found" when you might really want to send "301 Moved Permanently"?

The distinction seems small, but in certain cases it can actually make a big difference. For example, if you use a "301 Moved Permanently" response code, most search engines will remove the outdated link from their index and replace it with the new one. If you use "302 Found", they'll continue returning to the old page...

回答9:

Transfer is entirely server-side. Client address bar stays constant. Some complexity about the transfer of context between requests. Flushing and restarting page handlers can be expensive so do your transfer early in the pipeline e.g. in an HttpModule during BeginRequest. Read the MSDN docs carefully, and test and understand the new values of HttpContext.Request - especially in Postback scenarios. We usually use Server.Transfer for error scenarios.

Redirect terminates the request with a 302 status and client-side roundtrip response with and internally eats an exception (minor server perf hit - depends how many you do a day) Client then navigates to new address. Browser address bar & history updates etc. Client pays the cost of an extra roundtrip - cost varies depending on latency. In our business we redirect a lot we wrote our own module to avoid the exception cost.

回答10:

Response.Redirect is more costly since it adds an extra trip to the server to figure out where to go.

Server.Transfer is more efficient however it can be a little mis-leading to the user since the Url doesn't physically change.

In my experience, the difference in performance has not been significant enough to use the latter approach

回答11:

There are many differences as specified above. Apart from above all, there is one more difference. Response.Redirect() can be used to redirect user to any page which is not part of the application but Server.Transfer() can only be used to redirect user within the application.

//This will work.
Response.Redirect("http://www.google.com");

//This will not work.
Server.Transfer("http://www.google.com");

回答12:

Server.Transfer doesn't change the URL in the client browser, so effectively the browser does not know you changed to another server-side handler. Response.Redirect tells the browser to move to a different page, so the url in the titlebar changes.

Server.Transfer is slightly faster since it avoids one roundtrip to the server, but the non-change of url may be either good or bad for you, depending on what you're trying to do.

回答13:

Response.Redirect: tells the browser that the requested page can be found at a new location. The browser then initiates another request to the new page loading its contents in the browser. This results in two requests by the browser.

Server.Transfer: It transfers execution from the first page to the second page on the server. As far as the browser client is concerned, it made one request and the initial page is the one responding with content. The benefit of this approach is one less round trip to the server from the client browser. Also, any posted form variables and query string parameters are available to the second page as well.

回答14:

Just more details about Transfer(), it's actually is Server.Execute() + Response.End(), its source code is below (from Mono/.net 4.0):

public void Transfer (string path, bool preserveForm)
{
    this.Execute (path, null, preserveForm, true);
    this.context.Response.End ();
}

and for Execute(), what it is to run is the handler of the given path, see

ASP.NET does not verify that the current user is authorized to view the resource delivered by the Execute 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 Execute method and does not rerun authentication and authorization logic for the new resource. If your application's security policy 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 Execute method. Redirect 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 Internet Information Services (IIS) and ASP.NET security policy.

-from MSDN

回答15:

Response.Redirect involves an extra round trip and updates the address bar.

Server.Transfer does not cause the address bar to change, the server responds to the request with content from another page

e.g.

Response.Redirect:-

1. On the client the browser requests a page http://InitiallyRequestedPage.aspx
2. On the server responds to the request with 302 passing the redirect address http://AnotherPage.aspx.
3. On the client the browser makes a second request to the address http://AnotherPage.aspx.
4. On the server responds with content from http://AnotherPage.aspx

Server.Transfer:-

1. On the client browser requests a page http://InitiallyRequestedPage.aspx
2. On the server Server.Transfer to http://AnotherPage.aspx
3. On the server the response is made to the request for http://InitiallyRequestedPage.aspx passing back content from http://AnotherPage.aspx

Response.Redirect

Pros:- RESTful - It changes the address bar, the address can be used to record changes of state inbetween requests.

Cons:- Slow - There is an extra round-trip between the client and server. This can be expensive when there is substantial latency between the client and the server.

Server.Transfer

Pros:- Quick.

Cons:- State lost - If you're using Server.Transfer to change the state of the application in response to post backs, if the page is then reloaded that state will be lost, as the address bar will be the same as it was on the first request.

回答16:

Response.Redirect Response.Redirect() will send you to a new page, update the address bar and add it to the Browser History. On your browser you can click back. It redirects the request to some plain HTML pages on our server or to some other web server. It causes additional roundtrips to the server on each request. It doesn’t preserve Query String and Form Variables from the original request. It enables to see the new redirected URL where it is redirected in the browser (and be able to bookmark it if it’s necessary). Response. Redirect simply sends a message down to the (HTTP 302) browser.

Server.Transfer Server.Transfer() does not change the address bar, we cannot hit back.One should use Server.Transfer() when he/she doesn’t want the user to see where he is going. Sometime on a "loading" type page. It transfers current page request to another .aspx page on the same server. It preserves server resources and avoids the unnecessary roundtrips to the server. It preserves Query String and Form Variables (optionally). It doesn’t show the real URL where it redirects the request in the users Web Browser. Server.Transfer happens without the browser knowing anything, the browser request a page, but the server returns the content of another.