.NET Framework October 2019 Preview of Quality Rollup

Brett Lopez

Today, we are releasing the October 2019 Preview of Quality Rollup and Cumulative Updates for .NET Framework.

Quality and Reliability

This release contains the following quality and reliability improvements.


  • Addresses an issue with ValidationContext.MemberName when using custom DataAnnotation.ValidationAttribute.


  • Reduces the risk of returning unordered ConstructorInfo’s from Type.GetConstructors().
  • Improved behavior in scenarios where external bugs (such as a double-free) prevent underlying OS threads from starting. The runtime now fails with a diagnostic error rather than hanging waiting for the thread to start. This allows better failure recovery and better diagnostics of the problem that caused the failure.
  • Addresses and issue with late bound .NET COM calls containing SafeArrays where the SafeArray is not fully initialized.

Windows Forms

  • Addresses an issue that prevented navigation to the last item of the dropped-down menu item by single up-arrow key press.
  • Addresses and issue where the property grid can throw a NullReferenceException when selection changes to null (nothing is selected) in response to value changes


  • Addresses and issue where software rendering fails to draw images whose position and scaling are too large. For example, an Image element with Width=10, sourced to a bitmap with width=500 and positioned 700 pixels from the left edge of the enclosing window, fails to appear because the scaling factor S = 500/10 = 50 and the position X=700 are too large, in the sense that their product S * X = 50 * 700 = 35000 exceeds 2^15 = 32768.

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

Known Issues in this update


After applying this October 15th Preview of Quality Rollup for .NET Framework 4.8, some ClickOnce applications and applications creating the default AppDomain with a restricted permission set may observe application launch or application runtime failures, or unexpected behaviors. The observable issue is the System.AppDomainSetup.TargetFrameworkName (https://docs.microsoft.com/en-us/dotnet/api/system.appdomainsetup.targetframeworkname?view=netframework-4.8) is null, leading to any quirks enabling reverting back to .NET Framework 4.0 behaviors.


Customers observing new unexpected failures or functional issues can implement an application setting by adding (or merging) the following section to your application config file:

<?xml version="1.0" encoding="utf-8" ?>
          <AppContextSwitchOverrides value="Switch.System.Reflection.DoNotForceOrderOfConstructors=true" />


To resolve this issue install update for .NET Framework 4.8 for From December 2019 Security and Quality Rollup

Getting the Update

The Security and Quality Rollup is available via Windows Update, Windows Server Update Services, and Microsoft Update Catalog.

Microsoft Update Catalog

You can get the update via the Microsoft Update Catalog. For Windows 10, NET Framework 4.8 updates are available via Windows Update, Windows Server Update Services, Microsoft Update Catalog. Updates for other versions of .NET Framework are part of the Windows 10 Monthly Cumulative Update.

Note: Customers that rely on Windows Update and Windows Server Update Services will automatically receive the .NET Framework version-specific updates. Advanced system administrators can also take use of the below direct Microsoft Update Catalog download links to .NET Framework-specific updates. Before applying these updates, please ensure that you carefully review the .NET Framework version applicability, to ensure that you only install updates on systems where they apply. The following table is for Windows 10 and Windows Server 2016+ versions.

Product Version Cumulative Update
Windows 10 1809 (October 2018 Update) Windows Server 2019 Catalog 4520405
.NET Framework 3.5, 4.7.2 Catalog 4519569
.NET Framework 3.5, 4.8 Catalog 4519565
Windows 10 1803 (April 2018 Update)
.NET Framework 3.5, 4.7.2 Catalog 4519978
.NET Framework 4.8 Catalog 4519572
Windows 10 1709 (Fall Creators Update)
.NET Framework 3.5, 4.7.1, 4.7.2 Catalog 4520006
.NET Framework 4.8 Catalog 4519564
Windows 10 1607 (Anniversary Update) Windows Server 2016
.NET Framework 3.5, 4.6.2, 4.7, 4.7.1, 4.7.2 Catalog 4519979
.NET Framework 4.8 Catalog 4519562

The following table is for earlier Windows and Windows Server versions.

Product Version Security and Quality Rollup
Windows 8.1, Windows RT 8.1 and Windows Server 2012 R2 Catalog 4520408
.NET Framework 3.5 Catalog 4514371
.NET Framework 4.5.2 Catalog 4514367
.NET Framework 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2 Catalog 4519571
.NET Framework 4.8 Catalog 4519567
Windows Server 2012 Catalog 4520407
.NET Framework 3.5 Catalog 4514370
.NET Framework 4.5.2 Catalog 4514368
.NET Framework 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2 Catalog 4519559
.NET Framework 4.8 Catalog 4519566
Windows 7 SP1 Windows Server 2008 R2 SP1 Catalog 4520406
.NET Framework 3.5.1 Catalog 4507004
.NET Framework 4.5.2 Catalog 4507001
.NET Framework 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2 Catalog 4519561
.NET Framework 4.8 Catalog 4519568
Windows Server 2008 Catalog 4520409
.NET Framework 2.0, 3.0 Catalog 4507003
.NET Framework 4.5.2 Catalog 4507001
.NET Framework 4.6 Catalog 4519561

Previous Monthly Rollups

The last few .NET Framework Monthly updates are listed below for your convenience:


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