I have Visual Studio 2008 installed on a Windows 2008 Enterprise Server. I am thinking of upgrading to Visual Studio 2010 and wanted to know if this would be an in-place upgrade, or do I have to completely uninstalled Visual Studio 2008 then install 2010? What about all my solutions, do I have to upgrade them to 2010 as well?
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                A: 
                
                
              You can have both installed, and use them seperatly.
And only upgrade the projects you want.
                  EKS
                   2010-08-14 19:41:23
                
              Just to add to this, use your source control to keep the old 2008 version if for some reason you need to rollback.
                  j0rd4n
                   2010-08-14 19:43:38
                I do use SVN on all my code. But reversing the project is not a problem, visual studio actualy takes a backup.  Asuming your not gonna change .NET version downgrading visual studio will be easy.
                  EKS
                   2010-08-14 20:18:11
                
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                A: 
                
                
              
            To add to EKS there are some instances where you have to have side by side installation. Unmanaged C++/CLI code projects upgraded to VS2010 are forced to use .NET 4.0. So if you require to C+/CLI with .NET 3.5 or lower then you have to keep VS2008 around.
This is an issue that bit me and is really annoying.
Here is a Blog that describes the work around you have to make in order to use .NEt 3.5 etc and C+/CLI in VS2010
                  Peter M
                   2010-08-14 20:26:22