The Microsoft .NET Framework 4.5.1 is a highly compatible, in-place update to the Microsoft .NET Framework 4 and the Microsoft .NET Framework 4.5.
The web installer is a small package (less than 1 megabyte) that automatically determines and downloads only the components applicable for a particular platform. The web installer also installs the language pack that matches the language of the user’s operating system.
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
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What’s new in the .NET Framework 4.5.1?
The .NET Framework 4.5.1 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 options for this update
For more information about the various command-line options that are supported by this update, go to the "Command-Line options" section of the following MSDN website:
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.