Introducing .NET Framework 4.5 Beta

Introducing .NET Framework 4.5 Beta

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In September, we released the .NET Framework 4.5 Developer Preview. The Developer Preview was essentially a “feature complete” release, enabling you to “kick the tires” and otherwise get a good sense of what we were in the process of building for you. Across the many downloads of the Developer Preview, we expect that many of you tried a broad range of developer activities with the new pre-release version of the product, such as: using the new .NET Framework 4.5 features, trying out Visual Studio 11 Developer Preview and building proof-of-concept Windows Metro style apps. We send a big shout-out to the developers who submitted an app to the Windows 8 First Apps Contest. Thank you for all of your interest and support.

As you may have seen on Jason’s blog, we’ve now taken another step forward with .NET Framework 4.5, releasing .NET Framework 4.5 Beta and Visual Studio 11 Beta.

.NET Framework 4.5 Beta

At this point, most product features in the core of the .NET Framework are in a near-final state and are ready for you to take the proof-of-concept apps that you built with the Developer Preview and transform them into actual apps that you will make available to your customers. Obviously, you can update your existing .NET Framework 4 and 3.5 apps, too.

You can download .NET Framework 4.5 Beta now.

Take a look at What’s New in the .NET Framework 4.5 Beta to learn more about the new features.

Next on the .NET Blog

Over the next while, we will tell you the in-depth stories about a number of features that are included in the beta. We know that you will want much more inside information about the features that we’ve built, and what you can expect from them.

You can expect to see posts on the following topics shortly, and other topics will follow:

  • .NET Framework 3.5 Feature on Demand, on Windows 8
  • A response to the comments about in-place update releases
  • [What you care about goes here – post suggestions in the comments]

As always, we would like to hear from you. Please don’t hesitate to post a comment on the blog or at one of the forums that we monitor: Connect (report bugs), UserVoice (request features) and MSDN Forums (ask for help).

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  • so, why .net 3.5 on win 8 ?

    not .net 4.5

  • @ Vantsuyoshi, .NET Framework 4.5 Beta is installed by default on Windows Consumer Preview and on Windows Server “8” Beta.

    The .NET Framework 3.5 is not installed by default on Windows Consumer Preview and on Windows Server “8” Beta, it is installed by our “Feature on Demand”.

    Deonhe - MSFT

    Program Manager on .NET Framework

  • What are the known compatibility issue with installing .NET 4.5 (from the VS11 Beta) alongside previous .NET versions on a production machine?

    I would like to install both on my laptop, but as a developer I have to be sure that existing VS2010 projects will not be affected (I will not be porting them to VS11 yet if that makes any difference).

  • Since installing Dot Net 4.5 beta and VS2011 beta, one of my VS2010 projects receives this warning when compiling for every reference in the solution:

    C:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets(1546,5): warning MSB3270: There was a mismatch between the processor architecture of the project being built "MSIL" and the processor architecture of the reference "log4net, Version=, Culture=neutral, PublicKeyToken=1b44e1d426115821, processorArchitecture=MSIL", "AMD64". This mismatch may cause runtime failures. Please consider changing the targeted processor architecture of your project through the Configuration Manager so as to align the processor architectures between your project and references, or take a dependency on references with a processor architecture that matches the targeted processor architecture of your project.

  • @Martin Robins: Visual Studio 11 Beta does install .NET Framework 4.5 Beta which will perform an upgrade of .NET Framework 4 if it is currently on the machine where the installation is being done. A list of compatibility issues with .NET 4.5 Beta can be found here:

    Deonhe - MSFT

    Program Manager on .NET Framework

  • a good platform to develop web and service based applications

  • @Sam: Thank you for your feedback.   You describe an issue that I'm not familiar with.  Can you please file a connect bug against Dev11 using the following feedback link: and we'll make sure it gets routed appropriately?  

    Christine.Ruana - MSFT

  • @Sam its saying some of you references are set to x86, you need to recompile them as AMD64 or ANYCPU

  • @Sam

    That warning you are getting is by design. If your Any CPU project has a dependency on an architecture specific project or assembly, then the application produced is automatically not going to be Any CPU but instead the architecture of the dependency. If you continue to run your application anyway without aligning the targeted architectures of your project and its dependencies, then there could be runtime issues, which is why we pop this warning.

  • My last answer hasn't appeared here by the look of it. The issue is because the reference is installed into the GAC as two separate DLLs by Crystal Reports redistributable components. So there is a x64 and an x86 log4net DLL in the GAC.

  • Is there any way to suppress the warning?

  • I am unsure how the GAC aspect changes the validity of the warning. If the only references you can have are architecture specific, then your project also needs to target a specific architecture.

  • Hi Richa,

    This is a problem for us then using Crystal for VS2010. The Crystal Redistributable components install log4net DLLs into the GAC that are architecture specific with the same version as the log4net DLLs we are using but with a different public key. log4net DLLs are currently being published with 2 separate public keys however I do not know how to obtain a MSIL compiled version with same key as the one included in the Crystal installation.

    I haven't fully investigated but it might be an option to install the alternate public key log4net into the GAC as well if I can force our projects to use that version.

    As an aside, in normal operation, installing both the x86 and x64 log4net DLLs via the 2 separate Crystal Redist installs seem to work as expected so the warning does not seem relevant in this instance. We have a lot of projects that use this reference so suppressing the warning would be handy as it is adding a lot of "noise" to our build output atm.

    Kind regards,


  • What is the planned release date?  We are planning on upgrading to .NET 4.0 in the next month and want to know when 4.5 will be available to upgrade.

  • Nice and informative blog.

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