I thought I’d try out the Developer Preview of Visual Studio 2011 as I had heard there was round-tripping between VS 2010 and VS 2011. After opening a VS 2010 project in VS 2011, I was presented with the Visual Studio Conversion Wizard, which I thought was fine. I converted the project and started working. Trying to open the project in VS 2010, I was shown the Conversion Wizard again, and thinking this was normal went through the steps.
However, every time I would open the project in VS 2010, I would still get the Conversion Wizard. This was getting irritating so decided to do some spelunking into the .sln and .csproj files with Notepad2 to see what was up.
I noticed in the .csproj file in the first <PropertyGroup> section there is an element, <FileUpgradeFlags> which had a value of 40. I removed the value, so the entry is now <FileUpgradeFlags></FileUpgradeFlags>. Saving the .csproj file then opening in VS 2010, the Conversion Wizard doesn’t appear now, so I think the problem is solved.
Does anyone know why this happens? So much for using software that isn’t even in beta yet.