Hi Rene.
Reviewing all the conversation I did some testing. Created a wpf application, and changed references to point to .net 4.5. Added system.net and the command you try to run in a command button. Compilation fails in all senarios I tested. Also in one machine where I was testing beside I was changing references to point to .net 4.5, they remained to .net 4.0 (this one is using win 8.1)...
I believe that in your project the references you are using are for .net 4.0! I a previous post i put some screenshots which shows how to check that... For me every test I did, from migration to create a new project, I always ended using .net 4.0 after deployment. Never saw a reference to .net 4.5 in my deployed project!
I tend to believe that what Chris mentions, that pb 12.6 is .net 4.5 compatible but not really 100% aware, is the true. Actually I believe that pb 12.6 still uses .net 4.0 but has been tested to overcome some issues that pb 12.5 had with .net 4.5. At that point, if I'm wrong, I would appreciate if someone who is better informed than me corrects me.
What is really strange also is that for that question I haven't seen any reply from people working in pb support. Not to provide support, but simply to clarify if pb can create projects based on .net 4.5... Also I wonder what is the "Updated support for the .NET Framework v4.5" which is one of the announced changes for pb 12.6 (it's also mentioned in ISUG-TECH program and the Overview of Pb 12.6 scheduled for March 31, 2015). Is it only to make the product compliant with win8?
At that point I will simply add that if pb 12.6 cannot create projects using .net 4.5 (which at this point I do believe), it's a shock (at least for me). Maybe I misunderstood but I really thought it was in the new features.
Andreas.