February 24, 2021 - KB4601554 Cumulative Update Preview for .NET Framework 3.5 and 4.8 for Windows 10, version 2004, Windows Server, version 2004, Windows 10, version 20H2, and Windows Server, version 20H2
The February 24, 2021 update for Windows 10, version 2004, Windows Server, version 2004, Windows 10, version 20H2, and Windows Server, version 20H2 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. |
Common Language Runtime (CLR)
2 Windows Presentation Foundation (WPF)
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. See the Microsoft Update Catalog for instructions. |
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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