When opening an already existing solution in Visual Studio, it says
The C# project "..." is targeting ".NETFramework,Version=v4.5.2", which is not installed on this machine.
I have already tried
Official list of all targeting packs: https://www.microsoft.com/net/targeting. Make sure you download the "developer pack", not "runtime".
Direct links to offline installers: 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2
This problem seems to affect Visual Studio 2013 and Visual Studio 2015. The targeting packs are included in Visual Studio 2017.
Outdated links:
First, choose option 1, "Change the target to .NET Framework 4.5"
Next, go to the project options of the affected project, select "Application" and then choose "Install other frameworks..." from the list of target frameworks:
This brings you to a website where you can choose your version of Visual Studio and download the targeting pack (called developer pack).