How to enable .NET Framework 3.5 on Windows 8 or 2012

Install 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.

Enable the .NET Framework 3.5 in Control Panel

You can enable the .NET Framework 3.5 yourself through Control Panel. This option requires an Internet connection.
Press the Windows key Windows logo on your keyboard, type Windows Features, and press Enter. This brings up the Turn Windows features on or off dialog box. Alternately, open Control Panel, click on the Programs items, and then click on “Turn Windows features on or off” under Programs and Features.
Select the .NET Framework 3.5 (includes .NET 2.0 and 3.0) check box, press OK, and reboot your computer if prompted.

Step 1 :
Go to Settings. Choose Control Panel then choose Programs

Step 2 :
Click Turn Windows features on or off, and the user will see window as image below.

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

How to enable .NET Framework 3.5 on Windows 8 in Offline Mode

 if the user does not have an internet connection, this steps can not be applied.


The following are the steps to enable .NET Framework 3.5 (include .NET 2.0 and 3.0) feature in offline mode :

Step 1 :

Insert Windows 8 DVD or mount ISO image. The source of this feature can be found in folder E:\sources\sxs. (In this case E: the user’s drive letter on which the user has loaded Windows 8 Media.)

Step 2 :
Open CMD.EXE with Administrative Privileges. 

Step 3 :
Run the following command Dism.exe /online /enable-feature /featurename:NetFX3 /All /Source:E:\sources\sxs /LimitAccess, and hit Enter. 

After completing the installation of .NET Framework 3.5 you can see that the feature is enabled.

In Windows Server 2012 and for Windows Server 2012 R2

To use the Add Roles and Features Wizard, follow these steps:

1. Insert the Windows installation media.
2. Start the Add Roles and Features Wizard.
3. On the Select features page, select the .Net Framework 3.5 Features check box, and then click Next.
4. On the Confirm installation selections page, click the Specify an alternate source path link. The screen shot for this step is listed below.
   
5. On the Specify Alternate Source Path page, type the path of the SxS folder as a local path or as a network share path. The screen shot for this step is listed below.
   
6. Click OK.
7. Click Install to finish the wizard.