Hotfix rollup 3146709 for the .NET Framework 4.5, 4.5.1, and 4.5.2 in Windows

Prerequisites

To apply this hotfix, you must have the .NET Framework 4.5.2, 4.5.1, or 4.5 installed.

Restart requirement

You must restart the computer after you apply this hotfix if any affected files are being used. We recommend that you close all .NET Framework-based applications before you apply this hotfix.

Hotfix replacement information

This hotfix package doesn't replace a previously released hotfix package.

Issues that this hotfix rollup fixes

ASP.NET issue

Contention and bad performance on System.Web.BufferAllocator when you run a web application on computers that have more than 32 cores.

Fix: The contention has been eliminated by removing the global lock in System.Web.BufferAllocator.​

Windows Forms issue

The Windows Forms PrintPreviewDialog UI is initialized very slowly when the following conditions are true:

• A network printer is used.
• User preferences for this printer, such as duplex settings, are modified.

We added a performance optimization to this scenario. If page settings are not modified for a specific page, printer settings for this page are not reapplied (by accessing the printer spooler). If the application modifies printer settings by using the QueryPageSettings event handler, print preview generation performance for the affected pages is not improved, even if the opt-in flag is set.

In order to opt in to this optimization, the following key should be added to the app.config file, depending on your version of the .NET Framework.

NET Framework 4.5.2:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
   < appSettings >
       < add key="OptimizePrintPreview" value="true" />
   < /appSettings >
</configuration> 

.NET Framework 4.6 or a later version:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
 < runtime>
   < AppContextSwitchOverrides value = "Switch.System.Drawing.Printing.OptimizePrintPreview=true" />
 < /runtime>
</configuration> 

If an application can run on either version of the .NET Framework, use both switches in the same file.

To opt out, remove the switch, or set the values to false. ​

ClickOnce issue

ClickOnce has been updated to support TLS 1.1 and 1.2. ClickOnce automatically detects which TLS protocol is required at runtime. There are no extra steps required in the ClickOnce application to enable this.

Note ClickOnce continues to support TLS 1.0 for the foreseeable future, even though it is no longer considered PCI-compliant.​