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The Microsoft .NET Framework 4.5.1 Release Candidate (RC) is a highly compatible, in-place update to the Microsoft .NET Framework 4 and the Microsoft .NET Framework 4.5.

The offline package can be used in situations where the web installer cannot be used due to lack of internet connectivity. Wherever possible, Microsoft recommends you use the web installer instead of the offline package for optimal efficiency and bandwidth requirements.

More Information

Download information

The following file is available for download from the Microsoft Download Center:
Download Download the package now.

For more information about how to download Microsoft support files, click the following article number to view the article in the Microsoft Knowledge Base:

119591 How to obtain Microsoft support files from online services Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to the file.

What’s new in the .NET Framework 4.5.1 RC?

The .NET Framework 4.5.1 RC supports the writing of code in C#, Visual Basic, and F# programming languages, and includes these significant language and framework enhancements:

  • Better performance and reliability

  • ASP.NET application suspend and resume

  • On-demand compaction of the large object heap

  • 64-bit Edit and Continue

  • Activity tracing and sampling

  • SQL connection resiliency

  • Managed return values

For more information about these and other features of the .NET Framework 4.5.1, see the .NET Framework Developer Center website and blog post. This version of the .NET Framework runs side-by-side with the Microsoft .NET Framework 3.5 Service Pack 1 (SP1) and earlier versions, but performs an in-place update for the .NET Framework 4 and the .NET Framework 4.5.

Command-line switches for this update

For more information about the various command-line switches that are supported by this update, go to the "Command-Line options" section of the following MSDN website:

.NET Framework Deployment Guide for Developers

Restart requirement

You may have to restart the computer after you install this software if any affected files are being used. We recommend that you close all applications that are using the .NET Framework before you apply this update.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

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