I have a working solution that started as a visual studio forms web project and solution using 2010 version. I have progressed over the years to VS 2019 and I'm using the latest framework of 4.8.
However, my C# version is 5. I need to upgrade to C# 9 but it is not an option I can find in the project properties window. I would be grateful for some help.
I did try creating a blank solution in VS2019 and importing all the files. I did gain a project window with options I have not seen due to the newer project or solution version. I had 700 or so, errors on build and gave up. Perhaps if I had persevered.