System.Data.DataSetExtensions Config Error in Visual Studio 2008 RTM

I got the exception shown below when I opened an application that was developed under VS 2008:

ASP.NET runtime error: Could not load file or assembly ‘System.Data.DataSetExtensions, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089′ or one of its dependencies. The system cannot find the file specified

What’s happened is there is no more an assembly System.Data.DataSetExtensions with version number 2.0. There is a new version for the same assembly name under 3.5.0.0.

To resolve the problem, simply right-click on the web application, properties, then remove the reference to the 2.0.0.0 assembly.

Then, right-click on the web application solution, Add Reference, locate the System.Data.DataSetExtensions and add a reference to it. You may also need to update the entry web / app.config file under the <assemblies> tag. Update the version to 3.5.0.0

Failed to access IIS metabase

If you have both ASP.NET 1.1 and 2.0 on your machine you may encounter this issue. Upon running your website (via http://localhost/xxxx), you may encounter the error page that reports:

Failed to access IIS metabase

If so, you may have installed IIS after installing the .NET framework. If that’s the case, try repairing your ASP.NET installation. You can do this in one of two ways:

1. Control panel -> add remove programs -> .net install -> chnage/remove -> repair.
2. At a command prompt -> aspnet_regiis -i

If however you’re like me and installed VS 2003 / VS 2005 after IIS follow these steps:

1. Check that the appropriate ASP.NET version is associated with the virtual directory (Select VDIR –> Properties –> ASP.NET tab).

Dreaded: Unrecognized tag prefix or device filter ‘asp’

I have two masterpages, one nested inside the other. Once I had this error I was unable to use intellisense and controls wouldn’t be recognised in the code behind.

To fix this I did two things:

1. Deleted all files in: C:\Documents and Settings\[Username]\Application Data\Microsoft\VisualStudio\8.0\ReflectedSchemas
2. Kept the masterpages open in the ide when working on the page.

This fixed the problem for me.

These where helpful:
http://forums.asp.net/883002/ShowPost.aspx
http://blogs.msdn.com/mikhailarkhipov/archive/2005/04/21/410557.aspx