The other evening I was playing around with an ASP.NET Core application. When I started debugging it, I immediately saw an error message pop up that said
Unable to start program 'http://localhost:59676/'. An operation is not legal in the current state.
It was a bit of a head scratcher, so I decided to restart the debug session and see if the problem resolved itself. This didn't help and I saw the same error again.
This got me thinking.... if it is a feature, it must be able to be switched off.
Sure enough, the error message was gone.
Not a fix
While I agree that this isn't a fix, but more of a workaround... there is an investigation into the issue at the moment. Have a look at Chrome debugging crashes VS with "An operation is not legal in the current state." on the Developer Community Forum. Client-side debugging of web applications in Chrome is really a very nice feature and something I will definitely use. For now however, it seems that for my ASP.NET Core application I will have to wait a bit longer.
To read up more on debugging web applications client-side in Visual Studio 2017, have a look at an article introducing the feature: Client-side debugging of ASP.NET projects in Google Chrome