https://stackoverflow.com/questions/42692472/visual-studio-2017-error-unable-to-start-program-an-operation-is-not-legal-in

For me, the solution (workaround) is to turn off JavaScript debugging on Chrome, which I believe is a new feature introduced in VS 2017.

Go to Tools > Options > Debugging > General and turn off the setting for Enable JavaScript Debugging for ASP.NET (Chrome and IE).