I have VS2010 and VS2012 installed on my computer and had the .NET Framework 4.0 which I then upgraded to .NET Framework 4.5. However, I am still developing apps that need to work on .NET Framework 4.0. The project says that it is targeting .NET Framework 4 (Client Profile) the assemblies even point to .NET Framework 4.0 folder under Referenced Assemblies. The problem comes when I move this application to a machine that only has 4.0 it won’t start and come up with errors the immediate problem being an exception resulting from WindowState={Binding WindowState} which you can’t do in 4.0 but you can in 4.5. I need this to throw the exception on my development box, why doesn’t it? My assumption is that despite my best efforts is that it uses the 4.5 dlls if they exist. How can I make it really use 4.0 without uninstall 4.5?
Update
To repro this install .NET Framework 4.5 and create a WPF project targeting .NET Framework 4.0. Bind the WindowState to a property in a VM or code behind make this property have a public get and private set. .NET Framework 4.5 handles this just fine even when Mode=TwoWay must ignore the set .NET Framework 4 doesn’t and throws an exception: “A TwoWay or OneWayToSource binding cannot work on the read-only property ‘State’ of type…”. On the box with .NET Framework 4.5 works like a charm try it on a machine with only .NET Framework 4.0 and it blows up… So any ideas on how to really target 4.0 when 4.5 is installed?
Bug report to MS here: https://connect.microsoft.com/VisualStudio/feedback/details/774694/targeting-net-framework-4-0-when-4-5-doesnt-seem-to-work
This appears to be a bug in .NET Framework 4.5 and it should throw the exception but with .NET Framework 4.5 installed there is no way to have your application run on .NET framework 4.0 it will always use 4.5.
See this reported bug for more info:
http://connect.microsoft.com/VisualStudio/feedback/details/773682/wpf-property-with-private-setter-is-updated-by-a-twoway-binding