I have a 2010 project that is targeting .NET v3.5. Inexplicably I can no longer build v3.5 projects. The project doesn't have ANY references added. It won't even let me add a reference to System.Core as it is added by the 'build system'.
warning CS1685: The predefined type 'System.Func' is defined in multiple assemblies in the global alias; using definition from 'c:WindowsMicrosoft.NETFrameworkv4.0.30319mscorlib.dll'
IFilter.cs(82,49): error CS0433: The type 'System.Func' exists in both 'c:Program Files (x86)Reference AssembliesMicrosoftFrameworkv3.5System.Core.dll' and 'c:WindowsMicrosoft.NETFrameworkv4.0.30319mscorlib.dll'
Looks like something is grabbing onto 4.0 but I'm not quite sure how to fix it. Any one else run into this?
Coworker had this same issue. It took a reinstall of Windows to correct the problem
I've opened a bug on this one: https://connect.microsoft.com/VisualStudio/feedback/details/558245/warning-cs1685-when-compiling-a-v3-5-net-application-in-visual-studio-2010
If the compiler is set to verbose I see this:
FrameworkPathOverride = C:WindowsMicrosoft.NETFrameworkv4.0.30319
which is defined as:
Specifies the location of mscorlib.dll and microsoft.visualbasic.dll. This parameter is equivalent to the /sdkpath switch of the vbc.exe compiler.
Some other interesting tidbits: I've created a new project all together and cannot build v3.5 at all. I can build 2.0, 3.0, 3.5 Client Profile, 4.0 and 4.0 Client Profile with no problem. VB.NET can build v3.5 but C# cannot. I've tried a reinstall of .NET 3.5, 4.0 and Visual Studio 2010 with no success. Visual Studio debug logs shown nothing interesting and Safe Mode does not work.
Trying to avoid a Windows reinstall...
EDIT: I've come to realize others are facing this issue as well. Link, Link, Link
Reinstalled several times. Visual Studio uninstalls do not clean up after themselves. I've spun up a VM to develop on until I have a chance to reinstall my main OS.
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