If you are using the Windows operating system, the .NET
Framework may already be installed on your computer. Specifically, the
.NET Framework 4.5 is included with Windows 8 and installed on your
computer with the Windows 8 operating system. Similarly, the .NET
Framework 4.5.1 Preview is included with Windows 8.1 Preview.
However, if you install an app that requires a specific
version of the .NET Framework, the app's setup program might install the
.NET Framework on your computer or prompt you to install it. For
example, the .NET Framework 3.5 is not automatically installed with
Windows 8 or Windows 8.1 Preview. To run apps that require the .NET
Framework 3.5 on Windows 8 or later, you must enable version 3.5 on your
computer. There are two ways you can do this: by installing or running
an app that requires the .NET Framework 3.5 (that is, by installing the
.NET Framework 3.5 on demand), or by enabling the .NET Framework 3.5 in
Control Panel. Both options require an Internet connection.
In general, you should not uninstall any versions of the
.NET Framework from your computer, because an app you use may depend on a
specific version and may break if that version is removed. Multiple
versions of the .NET Framework can be loaded on a single computer at the
same time. This means that you do not have to uninstall previous
versions in order to install a later version.
Important notes:
-
Use the .NET Framework 3.5 for apps built for versions 2.0 and 3.0 as well as 3.5.
-
Installing a Windows language pack before installing
the .NET Framework 3.5 will cause the .NET Framework 3.5 installation to
fail. Install the .NET Framework 3.5 before installing any Windows
language packs.
-
Windows CardSpace is not available with the .NET Framework 3.5 on Windows 8.
Installing the .NET Framework 3.5 on Demand
If an app requires the .NET Framework 3.5, but doesn't
find that version enabled on your computer, it displays the following
message box, either during installation, or when you run the app for the
first time. In the message box, choose Install this feature to enable the .NET Framework 3.5. This option requires an Internet connection.
Prompt for installing the .NET Framework 3.5 on demand
Enabling the .NET Framework 3.5 in Control Panel
You can also enable the .NET Framework 3.5 yourself through Control Panel. In Control Panel, choose Programs and Features, choose Turn Windows features on or off, and then select the .NET Framework 3.5 (includes .NET 2.0 and 3.0)
check box. This option requires an Internet connection. You do not need
to select the child items for Windows Communication Foundation (WCF)
HTTP activation unless you are a developer who requires WCF script and
handler mapping functionality.
Turning Windows features on or off in Control Panel
Troubleshooting
If installing the .NET Framework 3.5 on demand or
enabling it in Control Panel fails, you may get one of the following
error messages:
-
0x800f0906: “Windows couldn't connect to the
Internet to download necessary files. Make sure that you're connected to
the Internet, and click Retry to try again.”
-
0x800F081F: “The changes could not be completed. Please reboot your computer and try again.”
These messages may be displayed for the following reasons:
-
Your computer is not connected to the Internet. Please connect, and then retry the operation.
If you cannot connect to the Internet, you can enable
the .NET Framework 3.5 by using the Deployment Image Servicing and
Management (DISM) command-line tool and specifying the installation
media (ISO image or DVD) you installed Windows 8 from.
-
In Windows 8 or Windows Server 2012, open a Command Prompt window with administrative credentials (that is, choose Run as administrator).
-
To install the .NET Framework 3.5 from installation media located in the D:\sources\sxs directory, use the following command:
DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:d:\sources\sxs
where:
-
/Online targets the operating system you're running (instead of an offline Windows image).
-
/Enable-Feature /FeatureName:NetFx3 specifies that you want to enable the .NET Framework 3.5.
-
/All enables all parent features of the .NET Framework 3.5.
-
/LimitAccess prevents DISM from contacting Windows Update.
-
/Source specifies the location of the files needed to restore the feature (in this example, the D:\sources\sxs directory).
For more information about DISM parameters and options, see How to Enable or Disable Windows Features
-
You are using a local source, but the network
location is inaccessible or doesn’t have the right content. Install the
.NET Framework 3.5 from installation media as described in the previous
bullet point.
-
Your administrator has configured your computer to
use Windows Server Update Services (WSUS) instead of Windows Update for
servicing. Ask your administrator to enable the policy to use Windows
Update instead of WSUS.
If these instructions do not correct the problem, download the paper Microsoft .NET Framework 3.5 Deployment Considerations from the Windows Dev Center for more extensive troubleshooting information.
