September 26, 2019 — KB4515871 Cumulative Update for .NET Framework 3.5 and 4.8 for Windows 10 version 1903 and Windows 10 version 1909

Applies to: .NET Framework

The September 26, 2019, update for Windows 10, version 1903 and Windows 10, version 1909 includes cumulative reliability improvements in Micorosoft .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 Prerequisites and Restart requirement sections.

Quality and reliability improvements


BCL1
  • Addresses an issue that affects thread contention that occurs in BinaryFormatter.GetTypeInformation by using ConcurrentDictionary to handle multi-thread access.
WPF2
  • Addresses an issue that affects a WPF ComboBox (or any Selector) within a DataGrid cell that can try to change its selection properties (SelectedIndex, SelectedItem, SelectedValue) when the cell's data item is re-virtualized or removed from the underlying collection. This can occur if the Selector's ItemSource property is data bound through the cell's DataContext setting. Depending on the virtualization mode and the bindings that are declared for the selection properties, the symptoms can include unexpected changes (to null) of the data item's properties, and unexpected displays (as null) of other data items that re-use the UI that was previously attached to the revirtualized item.
  • Addresses an issue in which a WPF TextBox or RichTextBox element that has spell checking enabled crashes and returns an "ExecutionEngineException" error in some situations, including inserting text near a hyperlink.
  • Addresses an issue that affects Per-Monitor Aware WPF applications that host System-Aware or Unaware child windows and that run on .NET Framework 4.8. This .NET version occasionally crashes and returns a "System.Collections.Generic.KeyNotFoundException" exception.
CLR3
  • Addresses an issue that might cause handle leaks to occur in scenarios that repeatedly load and unload Mscoree.dll.
  • Addresses rare cases that incorrectly cause process termination instead of delivering the expected NullReferenceException result.


1 Base Class Library (BCL)
2 Windows Presentation Foundation (WPF)
3 Common Language Runtime (CLR)

How to obtain and install the update


Install this update

This update will be downloaded and installed automatically from Windows Update.

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.

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.
 

Update replacement information

This update replaces previously released update 4511555 for Windows 10, version 1903.

How to obtain help and support for this update