You may or may not notice Windows 8 does not include .NET 3.5 (Which include .NET 2.0 and 3.0) Framework by default. But if the user is upgrading from Windows 7 to Windows 8, .NET Framework 3.5 will be fully enabled. The user can make sure whether this feature is enabled by checking in Program and Features.
Steps to Enable :
Go to Control Panel, Select ‘Small icons’ in ‘View By’ option & Click on ‘Program and Features’ link.
In ‘Program and Features’ window you could see ‘Turn Windows features on or off’ link located on left top of the window, Click on that.
On clicking ‘Turn Windows features on or off’, a window will appear like the one below
You could see .NET Framework 3.5 (includes .NET 2.0 and 3.0) option as Checked because I had already installed this feature. Since the installation is yet to happen, In your case it may not be checked/marked.
Enabling .NET Framework 3.5 With internet connection (Online Mode)
You can enable this feature by clicking on .NET Framework 3.5 (includes .NET 2.0 and 3.0) select it and click OK. After this step, it will download the entire package from internet and install the .NET Framework 3.5 feature. If you don’t not have an internet connection, this step cannot be applied.
Enabling .NET Framework 3.5 Without internet connection (Offline Mode)
You can still enable this feature in offline mode if you’ve Windows 8/8.1 DVD or ISO image. (In fact, Windows 8/8.1 Installation files)
Insert Windows 8/8.1 DVD or mount ISO image. The source of this feature can be found in folder D:\WINDOWS8.1\sources\sxs. (Assumption : D:\WINDOWS8.1\ is the root directory for the windows 8.1 Setup/Installation files )
Open Command line (CMD.EXE) with Administrative Privileges (Run as administrator)
Run the command Dism.exe /online /enable-feature /featurename:NetFX3 /All /Source:D:\WINDOWS8.1\ sources\sxs /LimitAccess, and hit Enter. That’s it. It’ll start installing* .NET Framework 3.5 in your PC.
*The installation time may vary depending upon the performance of your PC.
Hope this helped for you. Cheers..:)