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, 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.