While compiling the MEF Preview 5 source code on VS2010/.NET4.0,
I noticed a problem with System.Threading.LazyInit.
This is defined in the MEF source enclosed within #if !CLR40/#endif,
which should be defined for .NET 4.0 builds.
However, System.Threading.LazyInit does not exist in the
.NET 4.0 Framework (System.Lazy<T> does exist).
The obvious solution is to remove the #if !CLR40 (and the code
compiles and runs nicely), but the correct solution is ...?