Thursday, June 27, 2013

[.NET 4.5.1 - C#] New features in the .NET 4.5.1 and Visual Studio 2013 Preview

The next version of the .NET Framework is .NET 4.5.1. It has been published as Preview version as announced yesterday during the BUILD conference. This blog posts aims to present what has been added, modified and improved in this new Framework version.

The .NET Framework 4.5.1 Preview is the first update of .NET Framework 4.5. It contains critical fixes, improvements, and opt-in features and is part of the Visual Studio 2013 and Windows 8.1 Previews. But it is also available as direct download without the requirement of having an existing .NET Framework 4.5 installation.

Visual Studio 2013 and .NET 4.5.1 language based improvements

The following language based improvements that have been added to the Visual Studio 2013 and .NET 4.5.1 Previews :

  • X64 edit and continue is now possible (with some restrictions, but now X86 and X64 are nearly handled the same, which is good news)
  • Async/Await debugging has been added (such as support in the Call Stack window, Tasks window, etc…)
  • Managed return value inspection has been added (in the Autos and Watch windows it allows for easier return value debugging)
  • Windows Store application development improvements (compatibility with Windows 8.1, Win RT improvements, etc…)
  • ADO.NET idle connection resiliency has been added (rebuild broken idle connections with SQL databases automatically and transparently)
  • ASP.NET application suspension has been added (Idle sites are suspended from CPU activity and are paged to disk)
  • On-demand large object heap compaction (instruct the Garbage Collector to compact the large object heap, as part of the natural GC or a forced GC)
  • Multi-core JIT improvements (support for dynamically loaded assemblies)
  • Consistent performance after .NET Framework updates (application startup performance will be more consistent after a .NET Framework update)

Installation of Visual Studio 2013 and .NET 4.5.1

The installation of the .NET 4.5.1 Preview can be done by installing the Visual Studio 2013 Preview in which case it will be automatically installed with the Visual Studio components. Note that it will replace existing .NET 4.5 installations since it is an in-place upgrade.

  • Download the ISO for Visual Studio 2013 Ultimate Preview from here (you may also install any of the other version available if needed).


  • After downloading the ISO, you may now start the installation. The installation will require a high amount of empty hard disk space (in my example 14GB !!).

Install VS 2013    Install VS 2013 2

You may also just install the in-place upgrade directly on your test server without the full Visual Studio development environment. You can download it from here.

You are now ready to start you evaluation of the new features within Visual Studio 2013 Preview and .NET 4.5.1 Preview !

Future language upgrades now also possible via NuGet

Future language updates will be shipped via upgrades and service packs as it is already done today. They will also be available via component specific NuGet packages. This allows for a maximum of flexibility concerning your upgrade strategy. If you do not want to wait until language upgrades are fully available, you may partially upgrade your language components via NuGet packages depending on your specific customer needs.

Furthermore, you can now retrieve NuGet packages for the .NET Framework 4.5.1 and above on Windows Update (it will not work for earlier versions of the .NET Framework). This provides are very easy and efficient way of getting the latest upgrades for the packages that you use. Note that upgrades will only be serviced for NuGet packages that are actually used by your applications.


The .NET 4.5.1 Preview Framework update provides some fixes and multiple  performance enhancements. There are no major language features, but nonetheless those upgrades become very handy and will allow for a more seamless and productive software development experience. I think that the next big language features that we can expect will be around Roslyn, when it will finally be finished and shipped as RTM version. But we will see !


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