Imar,

PROBLEM: Chapter 14, ManagePhotoAlbum.aspx. On this page, insert a picture, this works fine. Then click the browser refresh and the same picture is inserted again. Repeat and it happens again.

CONTEXT: I wasn't entirely sure if it was something in my project. So I went to your site: http://aspnet4.planetwrox.com/ and I reproduced the error. If you look at album "testt", the duplicate images were produced by me clicking the browser refresh. To reproduce error, just insert an image and then click the browser refresh.

QUESTIONS: 1) Why does it happen? I looked at the code, life cycle, etc. and conceptually, I don't understand why it happens. 2) Can you provide a fix?

Thank you.

It's not a bug, it's by design. When you refresh, the browser will warn you about resubmitting the data, and that if you just made a purchase you should press cancel (that's at least what IE says) to avoid purchasing / paying again. You can work around it by implementing the PRG pattern (Post / Redirect / Get) where you redirect to the same page after saving the data, which issues a GET request for the same page. When users then hit refresh, they execute the GET request again which is harmless. For more info about PRG:

http://www.google.com/#hl=en&cp=21&g...t+get+redirect

Cheers,

Imar

__________________
Imar Spaanjaars
http://Imar.Spaanjaars.Com
Follow me on Twitter

Author of Beginning ASP.NET 4.5 : in C# and VB, Beginning ASP.NET Web Pages with WebMatrix
and Beginning ASP.NET 4 : in C# and VB.
Did this post help you? Click the button below this post to show your appreciation!