Installing the .NET Framework 3.5 on Windows 8 or 8.1
The .NET Framework is an integral part of many applications running on Windows and provides common functionality for those applications to run. For developers, the .NET Framework provides a consistent programming model for building applications. 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 is included with Windows 8.1. In other cases, you may need to enable the .NET Framework so that apps built against it can run.
There is no download for the .NET Framework 3.5 for Windows 8 or Windows 8.1. You must enable the .NET Framework 3.5 in Control Panel by following the instructions provided in this article.
For example, the .NET Framework 3.5 is not automatically installed with Windows 8 or Windows 8.1. 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.
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 may 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.
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
You can enable the .NET Framework 3.5 yourself through Control Panel. This option requires an Internet connection.
To enable the .NET Framework 3.5 in Control Panel
On the Start screen, type and then choose Control Panel. (To access the Start screen, press the Windows logo key on your keyboard.)
Choose Programs, and then choose Turn Windows features on or off.
Select the .NET Framework 3.5 (includes .NET 2.0 and 3.0) check box.
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.
The following video shows how to do this:
Updates installed. A common reason the .NET Framework 3.5 installation fails is because security update 2966826, 2966827 or 2966828 has been applied to a computer before the .NET Framework 3.5 was enabled. When this occurs, you may receive one of the following error messages.
0x800f0906 : “The source files could not be downloaded. Use the "source" option to specify the location of the files that are required to restore the feature. For more information on specifying a source location, see http://go.microsoft.com/fwlink/?LinkId=243077. The DISM log file can be found at C:\Windows\Logs\DISM\dism.log. Windows couldn't complete the requested changes.”
0x800F081F : “The source files could not be found. Use the "source" option to specify the location of the files that are required to restore the feature. For more information on specifying a source location, see http://go.microsoft.com/fwlink/?LinkId=243077. The DISM log file can be found at C:\Windows\Logs\DISM\dism.log”
To resolve this issue, install security update 3005628.
No Internet Connection. Another common error occurs if your computer is not connected to the Internet, you are using a local network source, but the network location is inaccessible or doesn’t contain the right files. You may receive an error message like the following:
“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.”
In this case, you should check your Internet connection and retry the operation. If you cannot connect to the Internet, you can enable the .NET Framework 3.5 .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 or other external drive) 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), and use the following command.
DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:installationMediaDrive:\sources\sxs
/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 (this mean you do not need Internet access).
/Source specifies the location of the files needed to restore the feature (for example, the D:\sources\sxs directory).
For more information about DISM parameters and options, see How to Enable or Disable Windows Features.
Windows Server Update Services. An error can also occur if 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, or you can try the following:
On your keyboard, press the Window key , and type gpedit.msc to start the Local Group Policy Editor.
Navigate to the Computer Configuration->Administrative Templates->System Folder and find the Specify settings for option component installation setting file.
Open the file and select Enabled. In the Options box, check the Contact Windows Update directly to download repair content instead of Windows Server Update Services (WSUS) option. Click OK to close the file.
Reboot your computer for the setting to take effect, if prompted to do so.
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.