How to upgrade .NET Framework?
First of all you need to install desired framework version on both development and client machines. Development machine is an environment where you code and build your project. It requires .NET Framework Developer Pack. Client machine is an environment where your application is used. It requires lighter package .NET Framework Runtime. Both types can be downloaded from Microsoft website.
When system is ready the next step is to change your project to target another framework version. Below you can see two methods how to do it.
Change target version with Visual Studio
Below example is created in Visual Studio 2017, however it should be the same or very similar in the other editions.
Open project Properties.
On Application tab find Target Framework combo box. By default it displays version of the framework which your project targets currently. On below example it is 4.6.
After opening the list we can see all versions available on the particular dev machine.
Let’s choose version 4.7.1 and Visual Studio warns us with below information.
After accepting it by clicking Yes the project is automatically reopened and ready for rebuild.
Change target version with text editor
Open project file (*.csproj) in text editor and find TargetFrameworkVersion node like the one below.
Change version number and save the file.
This is it. Your project is ready for rebuild.