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The February 27, 2020 update for Windows 10 Version 1903 and Windows Server 1903 RTM and Windows 10, version 1909 and Windows Server, version 1909 includes cumulative reliability improvements in .NET 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 Prerequisites and Restart requirement sections.
| CLR1 | - Addresses an issue with rare crashes or deadlocks that could occur if a GC occurs while another thread is running NGen'ed code which makes the initial call into a static method within the same module where one or more parameter types involve type-forwarded value types. - Addresses rare crashes that could occur if Server GC is enabled and a GC occurs while another thread is running NGen'ed code which is making the initial call into NGen'ed code in a 2nd module where one or more parameter types involve valuetypes defined in a 3rd module. - Addresses an issue with a crash that could occur in some configurations involving either hot-added CPUs or multi-group machines where per-group CPU count is not consistent across all groups. - Addresses an issue with a rare crash that can occur during the first call that native code makes into the managed portion of a mixed-mode DLL. |
| Workflow | - Addresses an accessibility issue where text inside a Windows Workflow Foundation Visual Basic Editor would use the wrong colors in high contrast themes. |
| Winforms | - Addresses an issue with interaction between WPF user control and hosting WinForms app when processing keyboard input. - Addresses an issue getting accessible objects for PropertyGridView ComboBox property items - adding the verification for item existence and validity. - Addresses an issue with WinForms ComboBox control reinitialization in AD FS MMC UI. |
| WCF2 | - Addresses an issue when using the WCFNetTcp binding. If a client stops responding during the connection handshake, sometimes a service will use the binding receive timeout instead of the open timeout. This update ensures that the correct open timeout is used during the entire handshake. |
1 Common Language Runtime (CLR)
2 Windows Communication Foundation (WCF)
Install this update
To download and install this update, go to Settings > Update & Security > Windows Update, and then select Check for updates.
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 .
To apply this update, you must have .NET Framework 3.5 or 4.8 installed.
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.
This update replaces previously released updates 4534132.
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