Server.Transfer Vs. Response.Redirect

Environment: ASP.NET, VB.NET, C#

If you read a lot of industry magazines and ASP.NET code samples, you may find that, although the majority use Response.Redirect to send the user to another page, some seem to prefer the rather mysterious-sounding Server.Transfer. So, what's the difference?

Well, Response.Redirect simply sends a message down to the browser, telling it to move to another page. So, you may run code like:

Response.Redirect("WebForm2.aspx")

or

Response.Redirect("http://www.karlmoore.com/")

to send the user to another page.

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").

This technique is great for wizard-style input forms split over multiple pages. But there's another thing you'll want to watch out for when using the preserveForm parameter. ASP.NET has a bug whereby, in certain situations, an error will occur when attempting to transfer the form and query string values. You'll find this documented at http://support.microsoft.com/default.aspx?id=kb;en-us;Q316920.

The unofficial solution is to set the enableViewStateMac property to True on the page you'll be transferring to, then set it back to False. This records that you want a definitive False value for this property and resolves the bug.

So, in brief: 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.

Top Tip: Don't confuse Server.Transfer with Server.Execute, which executes the page and returns the results. It was useful in the past, but, with ASP.NET, it's been replaced with fresher methods of development. Ignore it.

About the Author

Karl Moore (MCSD, MVP) is an experience author living in Yorkshire, England. He is author of numerous technology books, including the new Ultimate VB .NET and ASP.NET Code Book, plus regularly features at industry conferences and on BBC radio. Moore also runs his own creative consultancy, White Cliff Computing Ltd. Visit his official Web site at www.karlmoore.com.



About the Author

Karl Moore

Karl Moore (MCSD, MVP) is an experience author living in Yorkshire, England. He is the author of numerous technology books, including the new Ultimate VB .NET and ASP.NET Code Book (ISBN 1-59059-106-2), plus regularly features at industry conferences and on BBC radio. Moore also runs his own creative consultancy, White Cliff Computing Ltd. Visit his official Web site at www.karlmoore.com.

Comments

  • There are no comments yet. Be the first to comment!

Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • Today's agile organizations pose operations teams with a tremendous challenge: to deploy new releases to production immediately after development and testing is completed. To ensure that applications are deployed successfully, an automatic and transparent process is required. We refer to this process as Zero Touch Deployment™. This white paper reviews two approaches to Zero Touch Deployment--a script-based solution and a release automation platform. The article discusses how each can solve the key …

  • On-demand Event Event Date: December 18, 2014 The Internet of Things (IoT) incorporates physical devices into business processes using predictive analytics. While it relies heavily on existing Internet technologies, it differs by including physical devices, specialized protocols, physical analytics, and a unique partner network. To capture the real business value of IoT, the industry must move beyond customized projects to general patterns and platforms. Check out this webcast and join industry experts as …

Most Popular Programming Stories

More for Developers

RSS Feeds