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Release Date:



.NET Framework 3.5 and 4.7.2

Release Date:

.NET Framework 3.5 and 4.7.2

Improvements and fixes

This update includes quality improvements. No new operating system features are being introduced in this update. Important changes include:

  • Addresses an issue in System.Threading.Timer in which a single global queue that was protected by a single process-wide lock causes scalability issues in which timers are used frequently on multiple computers. You can opt in to the fix by using the following AppContext switch. (See these instructions to enable the switch.)

    • Switch name: Switch.System.Threading.UseNetCoreTimer

    • Switch value to enable: true

    • Note Don’t rely on applying the setting programmatically. The switch value is read only one time per AppDomain when the System.Threading.Timer type is loaded.

  • Addresses an issue that causes compatibility breaks that are seen in some System.Data.SqlClient usage scenarios.

  • Improves the memory allocation and cleanup scheduling behavior of the weak-event pattern. You can opt in to the fix by using the following AppContext switches. (See these instructions to enable the switches.)

    • Switch name: Switch.MS.Internal.EnableWeakEventMemoryImprovements

    • Switch name: Switch.MS.Internal.EnableCleanupSchedulingImprovements

    • Switch value to enable: true

  • Addresses an issue in .NET 3.5 Windows Forms applications that may not be able to render the application UI and, instead, render a white screen that contains a red "X" symbol. Additionally, it addresses a double prompt for the file save dialog box and folder browser dialog box.

Known issues in this update

Microsoft is not currently aware of any issues in this update.

How to get this update

Windows Update

To download and install this update, go to Settings > Update & Security > Windows Update, and select Check for updates.

Microsoft Update Catalog

To get the standalone package for this update, go to the Microsoft Update Catalog website.

File information

For a list of the files that are provided in this update, download the file information for cumulative update 4486553 for x64 and the file information for cumulative update 4486553 for x86.

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