June 27, 2019 — KB4502584 Cumulative Update for .NET Framework 3.5, 4.8 for Windows 10, version 1903 and Windows Server 1903 RTM

Quality and reliability improvements

• Improves the memory allocation and cleanup scheduling behavior of the weak-event pattern. To opt-in to these improvements, set AppContext switches to "true": Switch.MS.Internal.EnableWeakEventMemoryImprovements and Switch.MS.Internal.EnableCleanupSchedulingImprovements.

• Addresses an InvalidOperationException that can occur during weak-event cleanup, if called re-entrantly while a weak-event delivery is in progress.

• Addresses InvalidOperationException errors in System.Web.Hosting.RecycleLimitMonitor+RecycleLimitMonitorSingleton.AlertProxyMonitors. Worker processes for ASP.Net 4.7 and later are vulnerable to unexpected crashes because of this exception if the worker process consumes close to its configured Private Bytes recycling limit and application domains are being created or recycled (perhaps because of config uration file changes, or the presence of more than one application per worker process).

• Addresses an issue in which it was possible for a Workflow Service to get into a looping situation if an unhandled exception occurs during Cancel processing. To break this cycle, the Web.config file for the workflow service can have the following AppSetting specified that will cause the workflow service instance to terminate, instead of abort, if an unhandled exception occurs during Cancel processing:

<appSettings>
 <add key="microsoft:WorkflowServices:TerminateOnUnhandledExceptionDuringCancel" value="true"/>
</appSettings>

• Addresses multiple Accessibility and High DPI awareness improvements for Windows Forms and Windows Presentation Foundation (WPF) applications.

Known issues in this update

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

How to obtain and install the update

Install this update

To download and install this update, go to Settings > Update & Security > Windows Update, and 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.