I've installed recently announced Visual Studio 2017 RC and found out, that in old (VS2015) ASP.NET projects the
File->New->Project->ASP.NET Web Application
Visual Studio 2017 RC has updated the .csproj file of my web project with this:
<servers defaultServer="SelfHostServer"> <server name="SelfHostServer" exePath="" cmdArgs="" url="http://localhost:51775/" workingDir="" /> </servers>
I don't know why this happened, but deleting that solved my problem.