Announcing the .NET Framework 4.5.2

Announcing the .NET Framework 4.5.2

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Updated (July 2015): See Announcing .NET Framework 4.6 to read about the latest version of the NET Framework.

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.

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  • Great!

  • Great news!!!

  • Thank you for improving High DPI with WinForms. So far, High DPI with WinForms was a pain. Please keep on improving this.

    Your screen shots are a bit blurred, but it seems to me, the red error glyph is still 16x16 pixels (or 12x12, I don’t know), although scaled larger, and should have 32x32 pixels. One of the things I’d welcome is good support for icons/bitmaps with different resolutions for different DPI settings.

  • How will this work on Windows Azure cloud services? Will they need to push another osfamily version in order to update their .NET version, and if so, do you know when this is planned?

  • Chinese (Traditional) LangPack offline installer (NDP452-KB2901907-x86-x64-AllOS-CHT.exe) can't install on Windows 8.1 Hong Kong Edition (zh-hk).

  • Not able to install Chinese (Traditional) Language Pack on Windows 8.1 with Chinese (Hong Kong SAR) UI.

  • Woohoo! Is .NET native going to be supported for WinForms anytime soon?

  • QueueBackgroundWorkItem looks cool. I've installed .Net 4.5.2, how to I tell Visual Studio to use it? My listed frameworks only goes up to 4.5.1

  • @Coco and @Him: For Windows 8.1 with Chinese Traditional (Hong Kong), .NET 4.5.2 Chinese (Traditional) Language Pack would not install unless the OS Language Pack for Chinese Traditional (Taiwan) is installed. Please install Chinese Traditional (Taiwan) Windows 8.1 Language Pack to get unblocked on this.

    Preeti Krishna [MSFT]

  • @Peter: Thanks, for your feedback. You will need to install the .NET Framework 4.5.2 Developer Pack (link is in the blog post) so as to get .NET Framework 4.5.2 in the list of framework versions you can target to build applications.

    Preeti Krishna [MSFT]

  • Thank you!!!!!

  • I'm interested in HostingEnvironment.QueueBackgroundWorkItem - but don't understand exactly what "small" means in the following "lets you schedule small background work items". What are the limitations and where can I find the documentation?

  • Great News!...

  • Word of warning - this minor update will break any existing v4 application that relies on EnableViewStateMac being false (see here:  For a minor update I'm shocked that such a breaking change would be allowed.  This means that you cannot install the 4.5.2 update on a machine that has any v4 application requiring EVSM to be false.  I know it is a security hole but some older apps used it so it is still a breaking change.  Why MS didn't wait until the next major framework release is beyond me.

  • A new version has been released from them so that it now detects 4.5.2 as wel.

    You can download it here:

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