UnityVS error "The following files were specified on the command line"

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This happened when I grabbed a script from another project of mines put it into unity and tried to open it from there. Any suggestions how to fix it ?

Hey I had this same issue. I discovered that the problem was that I had forgotten to import the UnityVS package into this new Unity project. After doing so, this error message was fixed and no longer happened.

I hope this helps if you are still having problems!

It seems to be a problem again. Just installed Unity 2018.1.0f1 still in beta and I get this error with a new project. Very annoying. What I have found on the Visual Studio forum is to change the external script editor to MonoDevelop and back again. The problem is that there is no MonoDevelop anymore in Unity, I have changed it to “Open by file extension” and it seems to be working for me at the moment. It still opens it in the Visual Studio 2017. (I have installed latest “Visual Studio Tools for Unity”, it didn’t work.)
So step by step:

In Unity
—>Go to “Edit” tab
—>Go to “Preferences…”
—>On the left-hand side chose: “External tools”
—>And then change in the “External Script Editor” to “Open by file extension”

Scripts load up now properly.

if you click back on unity, it should notice the new file and regenerate the project. if not, try forcing a rebuild from the “Visual Studio Tools” drop down.

Thank you ,I forget it…

I was having this problem with Unity 2018.2.1f1, but updating Visual Studio Community 2017 to version 15.7.5 fixed it for me (I believe I was at 15.5.X before).