Announcing the .NET Framework 4.5.2

Announcing the .NET Framework 4.5.2

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We are happy to announce the availability of the .NET Framework 4.5.2. It is a highly compatible, in-place update to the .NET Framework 4, 4.5 and 4.5.1. You can download the releases now,

We incorporated feedback we received for the .NET Framework 4.5.1 from different feedback sources to provide a faster release cadence. In this blog post we will talk about some of the new features we are delivering in the .NET Framework 4.5.2.

ASP.NET improvements

  • New HostingEnvironment.QueueBackgroundWorkItem method that lets you schedule small background work items. ASP.NET tracks these items and prevents IIS from abruptly terminating the worker process until all background work items have completed. These will enable ASP.NET applications to reliably schedule Async work items.
  • New HttpResponse.AddOnSendingHeaders and HttpResponseBase.AddOnSendingHeaders methods are more reliable and efficient than HttpApplication.PreSendRequestContent and HttpApplication.PreSendRequestHeaders. These APIs let you inspect and modify response headers and status codes as the HTTP response is being flushed to the client application. These reliability improvements minimize deadlocks and crashes between IIS and ASP.NET.
  • New HttpResponse.HeadersWritten and HttpResponseBase.HeadersWritten properties that return Boolean values to indicate whether the response headers have been written. You can use these properties to make sure that calls to APIs such as HttpResponse.StatusCode succeeds. This enables shared hosting scenarios for ASP.NET applications.

High DPI Improvements is an opt-in feature to enable resizing according to the system DPI settings for several glyphs or icons for the following Windows Forms controls: DataGridView, ComboBox,
ToolStripComboBox, ToolStripMenuItem and Cursor. Here are examples of before and after views once this change is opted into.

.NET 4.5.1 Controls with High DPI setting .NET 4.5.2 Controls with High DPI setting

The red error glyph barely shows up and will eventually disappear with high scaling

The red error glyph scales correctly.

The ToolStripMenu drop down arrow is barely visible, eventually won’t be usable with high scaling

The drop down arrow in the ToolStripMenu scales correctly

Distributed transactions enhancement enables promotion of local transactions to Microsoft Distributed Transaction Coordinator (MSDTC) transactions without the use of another application domain or unmanaged code. This has a significant positive impact on the performance of distributed transactions.

More robust profiling with new profiling APIs that require dependent assemblies that are injected by the profiler to be loadable immediately, instead of being loaded after the app is fully initialized. This change does not affect users of the existing ICorProfiler APIs. Before this feature, diagnostics tools that do IL instrumentation via profiling API could cause unhandled exceptions to be thrown, unexpectedly terminating the process.

Improved activity tracing support in runtime and framework - The .NET Framework 4.5.2 enables out-of-process, Event Tracing for Windows (ETW)-based activity tracing for a larger surface area. This enables Application Performance Management vendors to provide lightweight tools that accurately track the costs of individual requests and activities that cross threads. These events are raised only when ETW controllers enable them.

For more information on usage of these features please refer to “What’s New in the .NET Framework 4.5.2”. Besides these features, there are many reliability and performance improvements across different areas of the .NET Framework.

Here are additional installers - pick package(s) most suitable for your needs based on your deployment scenario:

  • .NET Framework 4.5.2 Web Installer – A Bootstrapper that pulls in components based on the target OS/platform specs on which the .NET Framework is being deployed. Internet access is required.
  • .NET Framework 4.5.2 Offline Installer – The Full Package for offline deployments. Internet access is not required.
  • .NET Framework 4.5.2 Language Packs – Language specific support. You need to install the .NET Framework (language neutral) package before installing one or more language packs.
  • .NET Framework 4.5.2 Developer Pack – This will install .NET Framework Multi-targeting pack for building apps targeting .NET Framework 4.5.2 and also .NET Framework 4.5.2 runtime. Useful for build machines that need both the runtime and the multi-targeting pack.

Please install the .NET Framework 4.5.2 and let us know your feedback via UserVoice, Visual Studio Connect or as comment to this blog post. We’re also listening on Twitter and Facebook.

Leave a Comment
  • Please add 7 and 4 and type the answer here:
  • Post
  • The I cons on my systems bar, are to small, how do I enlarge them

  • @CoolDadTx If your page is internally facing only then yes, this is a bit of a problem. If your page is externally facing, this is a positive change and should be required.

    Nice to know though. Thanks for the post.

  • @Martin: Thanks, for your feedback. The red error glyphs with .NET Framework 4.5.2 (High DPI changes) are actually 48x48. The images have been scaled down for purposes of this blog.

    Preeti Krishna [MSFT]

  • @CoolDadTx: The EnableViewStateMac update has already been made available to .NET Framework 1.1 through 4.5.1 customers as of last December on Download Center with the security advisory - . Newer .NET releases automatically include all servicing updates including security updates for earlier versions in order to not regress customers that have installed the previous security update and then upgrade their .NET version.  

    Preeti Krishna [MSFT]

  • no bad, what are some of the new features ?

  • I had a compatibility issue when changing my app to 4.5.2: I get some errors saying that 'Forms' is not a member if 'Windows'.

  • Geez, guys.

    Even dummies know that using JPG for screenshots is BAD. You have to use PNG.

    How come you are unable to grasp it after the decades?

  • I like that you still improve Windows Forms components, though it could go beyond DPI improvements. The smaller and more frequent updates are also nice.

  • @andre_ss6: Please share the issue you are facing with repro steps by submitting a bug at - Thanks!

    Preeti Krishna [MSFT]

  • Lots of awesome WPF improvements in this release?

  • Great work!

  • We have some issues with using Web API routes that have custom paths in it, the paths are now escaped when there are characters such as spaces in it.  Were there any changes to this?  I was unable to find this anywhere.

    /controller/action/{path} where {path} = "hello/long path"

    4.5.1 we would get path = "hello/long path"

    4.5.2 we get an encoded path with %20, etc.

    our fix is to check version and decode accordingly, but it feels dirty.

  • Hi guys,

    I have just installed 4.5.2. Where can I take header for it with ICorProfilerCallback6 ?


  • Thank you for improving  activity tracing support in runtime and framework........Great news!!!

  • When will this be relesed into WSUS to update?

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