February 16, 2021-KB4601555 Cumulative Update Preview for .NET Framework 3.5 and 4.8 for Windows 10, version 1809 and Windows Server, version 2019

Release Date:
February 16, 2021

Version:
.NET Framework 3.5 and 4.8

The February 16, 2021 update for Windows 10, version 1809 and Windows Server, version 2019 includes cumulative reliability improvements in .NET Framework 3.5 and 4.8. We recommend that you apply this update as part of your regular maintenance routines. Before you install this update, see the Prerequsites and Restart requirement sections.

Quality and reliability improvements

CLR1

- Addresses an issue where the entire process would be torn down when a NullReferenceException propagated out of an exception filter.

- Addresses an issue with slowdowns that could occur when making large numbers of devirtualized calls into MarshalByRefObject-derived code.

WPF2

- Addresses an issue with lag responding to typing in TextBox, when spell-checking is enabled that was introduced in an update earlier this year.

- Addresses an issue with a leak of touch-related resources, including OS handles, when closing a window. The leak only occurs when a touch device is active, and only for windows whose HwndSource is created directly by the app.

- Addresses a crash when docking a window within Visual Studio, or, more generally, disposing an HwndSource whose RootVisual is null.

Winforms

- Addresses an issue in ComboBox drop down item bounding rectangle as exposed to the accessibility tools, where we did not take into account that some items might be scrolled out of view, we had always started counting items from the first visible one, and thus item rectangle location was incorrect.

- Implemented ScrollItemPattern (IScrollItemProvider (uiautomationcore.h) - Win32 apps | Microsoft Docs) for ComboBox drop down items.

1 Common Language Runtime (CLR)
2 Windows Presentation Foundation (WPF)

Additional information about this update

The following articles contain additional information about this update as it relates to individual product versions.

  • 4602298 Description of the Cumulative Update Preview for .NET Framework 3.5, 4.7.2 and 4.8 for Windows 10, version 1809 and Windows Server, version 2019 (KB4602298)

How to get this update

Install this update

Release Channel

Available

Next Step

Windows Update and Microsoft Update

Yes

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

Microsoft Update Catalog

Yes

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

Windows Server Update Services (WSUS)

No

You can import this update into WSUS manually via 4602298. See the Microsoft Update Catalog for instructions.

File information

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

Prerequisites

To apply this update, you must have .NET Framework 3.5 or 4.8 installed.

Restart requirement

You must restart the computer after you apply this update if any affected files are being used. We recommend that you exit all .NET Framework-based applications before you apply this update.

How to obtain help and support for this update

Known issues in this update

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

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