Please select a valid startup item

Question

I have migrated from Visual Studio 2008 to VS 2017.

I am getting this error when I try to run project with the green play button:

Obviously I have to select a valid startup item, but there are two pieces of information I need to do that:

1. what are typical valid startup items that I can try to select?

2. How do I select them?

I am a long time developer, but I am new to visual studio so please give me instructions based on terminology I can see on the screen.

Answer 1

It might be the case that you have opened your project using

File->Open->Folder 

Use the right method to open your project using

File->Open->Project/Solution 

or

File->Open->Website 

Answer 2

File > New > Project From existing code. Select type of project > Next. Enter project name > Finish.