.NET Framework 3.5 Affects 2.0

I have installed .NET Framework 3.5 along with already existing 2.0 as a part of Visual Studio .NET 2008 installation. What a surprise it was to find out that the old "web site" projects were all broken... after a few hours of investigation, my coworker, Glen and I have found that the 3.5 is not so innocent and  it writes to 2.0 new version of assemblies. Why in the world it would do it?! So far this is under MS engineers investigation and I hope it was an error on our side.

And this KB can be useful for some people as well: KB941824 - at the 'cause' section, in little font I loved the note: "When you install the .NET Framework 3.5, the .NET Framework files in the V2.0.50727 folder are updated. Therefore, when you install the .NET Framework 3.5, Visual Studio 2005 is affected."  Great...

2007-11-28 21:25 Update: a quick example of breaking code is attached in zip file. The problem is in RuntimeMasterPageFile property at compile time. Issue20071128.zip 

2007-11-30 00:15  Update: after recreating the whole environment step by step I reproduced the issue and seems like the breaking change is in web.config under  system.web section - one of the configurations, <page> has an attribute pageBaseType that I was using and didn't have to specify anything on each single page. After 3.5 install, which is also a SP1 for 2.0, this feature is no longer respected by compiler. Keep tuned for updates.

2007-12-03 Update: ASP.NET team confirms that this is a bug in 3.5  (2.0 SP1) and they will release a hotfix within up to 4 weeks.

2008-03-05 Update: The fix was built, but failed one of MS internal test stages. Therefore, they have moved it back to the previous stage for rebuilding. Updates on the status will be posted as that process continues.


  • The HTML Table issue you referenced above was fixed for the final .NET 3.5 release - so you shouldn't be seeing an issue with that.

    Can you send me an email (scottgu@microsoft.com) on what you did encounter problems with? We aren't aware of any known breaking issues right now.



  • @Scott,

    Thanks for quick involvement - have sent you the file.
    This is not happening with Web Application Project based applications, but only with Web Site ones.


  • FYI, the reason it updates 2.0 files is because 3.5 requires 2.0 SP1, which is installed along with the 3.5 files.

  • I can confirm the problems you have. We have exactly the same issues when we installed .NET 3.5 on our VS2005 machines. Visual Studio thought all references were broken for our 2.0 projects, so it wouldn't compile. Uninstalling 3.5 and reinstalling 2.0 and 3.0 fixed our problems.

  • @Robert

    Your assumption is incorrect, all those machines had SP1 installed on them. Besides that, the point is that 3.5 installation should not deliberately update the 2.0 files, unless it is well known fact and stated properly. And above that, what's in the simple code that I supplied that would be not accepted by 2.0 SP1 if you think thats the reason?


    We filed an issue with MS support and also as you can see Scott Guthrie is on case. Thanks for the confirmation.

  • Sean,

    I think this is what you should have in the aspx:

    Note that I have the CodeFileBaseClass attribute. This compiles fine for me.

    Raj Kaimal

  • @Raj

    Great workaround! Thanks for the tip. At this point at least i can get the work done, but still Microsoft has to solve the issue and find out what is it. The workaround just indicates there's a problem below the surface.


  • Anybody know what ever happened with this? I can't find a relevant hotfix anywhere.

  • @Max,
    they are still trying to fix it. I guess not enough people have complained (opened issue logs) and it's not given a higher priority. I will update the post with details.

  • Can you please update this issue, my friend?

    or do you want some rice? rice, rice rice?

  • @Indian Friend,
    sorry, but I cannot as I moved on. Plus we switched from "web site" projects to "web application" projects entirely.

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