Microsoft .NET Framework 4.5 Readme

Date Published: September 28, 2012

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1. .Net Known Issues

1.1 NetFx Installation

1.1.1 The .NET Framework 4.5 language packs are not available on Windows 8

The .NET Framework 4.5 language packs cannot be installed on the Windows 8 operating system, because the .NET Framework 4.5 is a component of the operating system. The .NET Framework 4.5 language packs can be installed on earlier supported versions of Windows.

To resolve this issue:

Download the language packs for the Windows 8 operating system, or install a localized version of Windows 8 to get the localized resources for the .NET Framework 4.5.

1.1.2 Failed or canceled .NET Framework 4.5 installation reverts application pools to 2.0

If you are upgrading from the .NET Framework 4 to the .NET Framework 4.5 RTM release, and if the installation is canceled or fails, the .NET Framework reverts to version 4. However, ASP.NET 4 is also unregistered and all the application pools in IIS are set to target the .NET Framework 2.0.

If this happens, browsing to a web application based on ASP.NET 4 results in a configuration error that reports that the "targetFramework" attribute of the "compilation" element is not recognized.

To resolve this issue:

To work around this issue:

  1. Fix the incorrect registration by completing option A or option B below (you do not have to do both):

  2. Additionally, if you have custom application pools that targeted ASP.NET 4 before the failed upgrade, use IIS Manager (inetmgr.exe) to manually reset them to target ASP.NET 4.

1.2 NetFx Uninstallation

1.2.1 ASP.NET 2.0 and 3.5 donít work after you remove the .NET Framework 4.5 from Windows 8 or Windows Server 2012

On Windows 8 and Windows Server 2012, ASP.NET 2.0 and 3.5 require the ASP.NET 4.5 feature to be enabled. If you remove or disable the .NET Framework 4.5, your ASP.NET 2.0 and 3.5 applications will no longer run.

To resolve this issue:

On Windows 8

Enable the ASP.NET 4.5 feature in Control Panel:

  1. Open Control Panel.
  2. Choose Programs.
  3. Under the Programs and Features heading, choose Turn Windows features on or off.
  4. Expand the node .NET Framework 4.5 Advanced Services.
  5. Select the ASP.NET 4.5 check box.
  6. Choose OK.

On Windows Server 2012

See IIS 8.0 Using ASP.NET 3.5 and ASP.NET 4.5 in the IIS Learning Center.

1.3 .Net Product Issues

1.3.1 General Issues

There are no known issues.

1.3.2 ASP.NET

There are no known issues.

1.3.3 Winforms

There are no known issues.

1.3.4 Parallel Programming

There are no known issues.

1.3.5 Managed Extensibility Framework

There are no known issues.

1.3.6 Entity Framework

There are no known issues.

1.3.7 LINQ to SQL

There are no known issues.

1.3.8 Windows Communication Foundation (WCF) Problems running existing XML serialization code in WCF 4.5

In Windows Communication Foundation (WCF) 4.5, the XmlSerializer class was optimized to remove its dependency on the C# compiler. This change provides significant performance gains for cold startup scenarios. However, it may cause problems in XML serialization code that was compiled in WCF 4 but is running against WCF 4.5.

To resolve this issue:

If you encounter any problems running your existing XML serialization code in WCF 4.5, use the following configuration element to revert to the XmlSerializer behavior in WCF 4:

      <xmlSerializer useLegacySerializerGeneration="true"/>

1.3.9 Windows Presentation Foundation (WPF)

There are no known issues.

1.3.10 Windows Workflow Foundation (WF) Host fails to start if you use workflows with the Workflow Identity parameter

The .NET Framework 4.5 includes a new workflow parameter, Workflow Identity, that is persisted to the SQL Workflow Instance Store. If you use workflows that include this parameter and its value is not null, you must update the Instance Store so it can store the value. Otherwise, the host will fail to start.

To resolve this issue:

Update the SQL Workflow Instance Store by running the script at the following location:

%windir%\Microsoft.NET\Framework\<version>\SQL\<language>\SqlWorkflowInstanceStoreSchemaUpgrade.sql Some of the new features in the Workflow Designer may cause issues with existing solutions

In the .NET Framework 4.5, the Workflow Designer includes the following changes:

To resolve this issue:

Use the workaround for each issue discussed in the preceding list.

2. .Net Maintenance

2..1 Upgrading to Windows 8 does not update .NET Framework 4 language packs

If you upgrade from the Windows 7 operating system to Windows 8, the .NET Framework 4 language packs that you previously installed on your computer are not removed or updated. This issue affects language packs that do not match the language of the upgraded Windows 8, not including English. For example, if you have an English edition of Windows 7 Ultimate and the .NET Framework 4 German language pack, and you upgrade your system to the English edition of Windows 8, the language pack will remain on your system but will not be updated to the .NET Framework 4.5.

To resolve this issue:

Either uninstall the .NET Framework 4 language pack before you upgrade to Windows 8, or install the appropriate Windows 8 language pack after you upgrade.

3. Related Links

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