Hi Ahmed;
Can you try deleting the entire "output directory" and its contents & trying again?
Failing that ...
1) Make sure that .Net 3.5 / 4 or 4.5 is not installed. If they are installed ... make sure that they are not in the system Path. PB 11.x only works with .Net 2.0.
2) Make sure that the .NET 2.0 SDK is installed & registered in the System Path.
Regards .... Chris