Install Microsoft .NET Framework 4.5 or 3.5.1 on Windows 7

Microsoft .NET Framework version4.5 or 3.5.1 is included with Windows 7,8 & 10. Follow the steps below to enable it.
If you try to run .NET 4.5 or 3.5 installer downloaded from the Microsoft website on Window 7, you will receive the following error: You must use "Turn Windows features on or off" in the Control Panel to install or configure Microsoft .NET Framework 4.5 or 3.5 SP1. Instead of running the installer, follow the instructions on this page.

Note: The same steps work for Windows 8 and Windows 10.

1. Click Start -> Control Panel 

2.  Click Programs

3. Click Turn Windows features on or off

4. Click the check-box next to Microsoft .NET Framework 3.5.1 

 5. You will see the check-box become filled

 6. Click OK

7. Wait for Windows to complete the operation. If it asks you to connect to Windows Update  download required files, click Yes. 

 8. Click Download file from Window Update.

 9. Wait for the Download process to complete.