Differences between ASP.Net framework 1.x and 3.5 / websites and web applications. Things to consider during a migration

We recently migrated a large ASP. website from framework 1.1 to framework 3.5 and in the process also migrated from a website to a web application.

On the surface everything seemed to work fine, but now we are discovering that none of the "pages" are doing what they used to.

The site 开发者_JAVA技巧is made up of one default.aspx page that loads all the "pages" as user controls. (I am guessing this was to achieve the same effect as having a master page before master pages were invented.)

I think we missed a trick (or twelve) during the migration. What are the big stumbling blocks that other people have experienced

Update We managed to find the problem that was making our pages stop working, but can not figure out why: When we cleaned up the code of the main page, we added whitespace (a newline) between the open and closing tags of the control that all the other "page" user controls get loaded into. Once we removed the newline everything started working again. Can anyone explain this?

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I have experienced problems during manual copying etc. that has lost the connection between the GUI controls and the event-methods in the code behind. There are differences between the different versions of ASP.NET on how the event handling is coupled, and there are even more than one way of doing it (automatic based on names or explicit in code), and this is easy to mess up when changing from one "standard" to another, which is what you do converting to a differen version of .NET. It is also an additional source of confusion for Visual Studio when you also converted from Web Site to Web Application.

I am guessing that the trick was just to do some editing in Visual Studio, and VS might have automagically re-attached event handlers etc.

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One things you should know is that if your new server is 64 bit. There is a chance that the controls on the page will be loaded concurrently with the page. In a sense there will be a lot of timing issues. If you are not using 64 bit server however this is not relevant.