Visual Studio 2017 error: Unable to start program, An operation is not legal in the current state

After fresh installation of Visual Studio 2017 I tried to run .NET Core Web project and when trying to run it on Chrome I am getting this error:

Unable to start program, An operation is not legal in the current state

Solution 1:

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).

VS2017 Disable JS Debugging

This is a known issue already, and seems to have an investigation underway.

Full information about JS debugging in VS 2017 here: https://blogs.msdn.microsoft.com/webdev/2016/11/21/client-side-debugging-of-asp-net-projects-in-google-chrome/

Solution 2:

Today I got this error, and I just did a small workaround which was too simple.

Close all of your chrome instances, that you might have opened before you opened Visual Studio.
Now stop debugging and run your application again.

You will not get the error again and if the debugger doesn't hit, refresh the browser again.

Update (12-Dec-2018):

I just tested this bug in Visual Studio 2019 preview, it seems like the bug is fixed now.

Hope this helps.

Solution 3:

I had the same problem after the most recent VS 2017 update (released March 14, 2017: build 26228.09). My program would debug fine in IE but would bomb out in Chrome. Killing all instances of Chrome within the Windows command line fixed the problem for me.

taskkill /im chrome.exe /f

I was then able to debug in Chrome.

Solution 4:

3 options

Turn off the JavaScript debug feature in Tools > Options > Debugging > General
Kill all chrome tasks
Switch to another browser to debug

Solution 5:

I found a workaround to this which worked for me.

With Chrome selected as your browser, click the Debug menu and select Attach to Process....

In the subsequent dialog, select Chrome.exe in the list and click the Select button for Attach to:. Tick the Native box, then Attach (or just double-click Chrome.exe): enter image description here

This starts the project running without launching the browser. Stop and restart in Chrome and the error is gone.

Of course, another potential solution is to use a different browser but I like debugging in Chrome. :-)