An Error Occurred Attempting to Determine the Process Id of Dotnet.Exe Which Is Hosting Your Application. One or More Error Occured

An error occurred attempting to determine the process id of dotnet.exe which is hosting your application. One or more error occured

An error occurred attempting to determine the process id of dotnet.exe which is hosting your application. One or more errors occurred.

That problem can occur when three things are true:

your app is trying to run with SSL,
your app does not have an SSL Certificate setup, and
you are debugging your app (which is preventing SSL certificate setup).

As a quick fix attempt, run the app without debugging via Ctrl + F5 or view the app in the browser via Ctrl + Shift + W. That might install the SSL certificate for you. If it does not, consider changing your app's launch settings from HTTPS to HTTP. If you really need SSL, you'll have to figure out how to install and use an SSL certificate on your local machine.

Checkout out these on GitHub and StackOverflow.

https://github.com/aspnet/Home/issues/1608
https://github.com/aspnet/Home/issues/1723
https://github.com/Azure-Samples/active-directory-dotnet-webapp-openidconnect-aspnetcore/issues/17
An error occurred attempting to determine the process id of the DNX process hosting your application on clean installed windows 10 + vs2015

An error occurred attempting to determine the process id of dotnet.exe

I think I've just figured out what it is... It is happening only when the VPN is active. If I disconnect the VPN it works again. I don't know a solution of how to get it to work whilst the VPN is active, but I am happy enough with the work around for now.

This may come in useful in future to anybody else who has been stuck in the same position. For me the confusion of it sometimes working and sometimes not is because I have to activate and deactivate the VPN to connect to certain things.

Can't Start IIS Express: An error occurred attempting to determine the process id

Uninstall and re-install of IIS Express fixed it.

Turns out port 44300 wasn't bound to my IIS Express cert. Bill Hiebert figured it out as documented in this developer community issue.

When I ran netsh http show sslcert, port 44300 wasn't listed. I uninstalled and re-installed IIS Express and now it is listed.

SSL Certificate bindings: 
------------------------- 

IP:port                      : 0.0.0.0:44300
Certificate Hash             : somevalue
Application ID               : {someid}
Certificate Store Name       : MY
Verify Client Certificate Revocation : Enabled
Verify Revocation Using Cached Client Certificate Only : Disabled
Usage Check                  : Enabled
Revocation Freshness Time    : 0
URL Retrieval Timeout        : 0
Ctl Identifier               : (null)
Ctl Store Name               : (null)
DS Mapper Usage              : Disabled
Negotiate Client Certificate : Disabled
Reject Connections           : Disabled
Disable HTTP2                : Not Set

An error occurred attempting to determine the process id of the DNX process hosting your application

For me the problem was solved by closing down Visual Studio, deleting

project.lock.json

and starting Visual Studio again.

Edit: I was using RC1.

An error occurred attempting to determine the process id of the DNX process hosting your application on clean installed windows 10 + vs2015

The poster has stated that they found the answer to their question but I experienced the same error message with RC1 and the accepted answer did not resolve my issue. I see that Sven Gillis is still hunting for a solution as well so I'd like to share what solved the issue for me.

Turns out that the error can be triggered by a bug in RC1 Update 1 (and all prior versions) which occurs if the installation is being used via a windows login name that has a space in it. e.g. "Tim Smith".

I was not able to find a patch but there is a work around. Just create another user account on the machine that doesn't have a space in it (e.g. "Tim") and to use visual studio under that account. In my case this solved the issue. I can now create web projects in Visual Studio 2015 Community Edition Update 1 via the Asp.Net 5 templates and can run them via F5 and Ctl+F5 from within visual studio and I no longer receive the error.

However if I switch to the original user account on the machine that has a space in it, I still receive the error when trying to run a project generated from the same template. Same code ran from two different windows user accounts producing two very different results. I hope this helps someone else, I wasted 7 full days hunting for the solution to this issue.