The error "This project is incompatible with the current version of visual studio" displayed

Question

I installed Vs 2010 Express in my PC, and created a poject named myproject with .net 4.0, it works well in Vs 2010 Express.

Now I installed Vs 2012 Express in my PC, and open the project myproject and upgrade it to .net 4.5, it wells well in Vs 2012 Express too.

I delete the project myproject all files, then restore it from my old backup file, when I try to open the project from Vs 2010 Express, I get the following information.
"This project is incompatible with the current version of visual studio", why?

How can I open the project in Vs 2010 Express? I guess the Vs 2012 Express maybe mark the project as .net 4.5 and stored the information in the somewhere of hard drive. Although I restore the project myproject from old backup file, Vs 2010 Express still think it is a project of .net 4.5.

Thanks!

Answer 1

If the message "This project is incompatible with the current version of Visual Studio" is due to an attempt to open a project targeting .Net 4.5 with Visual Studio 2010, then the "solution" or workaround is to edit the .csproj file and change the TargetFrameworkVersion from "v4.5" to "v4.0". That at least allows the project to be loaded, although it may result in compiler errors if the program is dependent on 4.5 features.