How to install .NET Framework 3.5 SP1 into Visual Studio 2017
You should install the .NET 3.5 development tools using the Visual Studio Installer.
Instructions:
- Close Visual Studio (the next step will close it for you, but it's better to close it yourself so you are in a known state).
- Open the Visual Studio Installer (search for it in the Start menu).
- Choose to modify the installation you desire.
- Go to the "Individual Components" tab.
- Under the ".NET" section choose ".NET Framework 3.5 Developer Tools".
- Click "Modify" in the bottom right corner to apply the changes.
You may also need to turn on the Windows Feature .Net Framework 3.5 (includes .NET 2.0 and 3.0).
I had the same issue. Go to Windows Control panel over there add features to windows. Then check .NET framework 3.5. Done! https://improveandrepeat.com/2018/07/an-alternative-way-to-install-net-3-5-on-windows-10/
(you should also check if you already haven't ".NET 3.5 development tools" using the Visual Studio Installer.)