Visual Studio 2017 install breaks Visual Studio 2015 ASP.NET Core Projects

asp.net Core .Net Core Visual Studio-2017

asp.net Core Problem Overview

After installing Visual Studio 2017 Professional I can't build my ASP.NET Core in Visual Studio 2015 Professional anymore. I never opened this project in VS2017

I get >The following error occured attempting to run the project model server process (1.0.0-preview3-004056). > >Unable to start the process. No executable found matching command dotnet-projectmodel-server

I then created a brand new ASP.NET Core project in Visual Studio 2015 and I get the exact same message when loading my project.

Additionally when I want to build the project I get

>MSB1009: Project File does not exist.

The same problem does not occur with ASP.NET 5 projects so It's only limited to ASP.NET Core

Visual Studio 2017 7 March Update

Ifa global.json is added like in the answers below get an error message for any .net framework version used in the global.json and that exist in the C:\Program Files\dotnet\sdk\ folder

>Error MSB4019 The imported project "C:\Program Files\dotnet\sdk\X.X.X\Microsoft\VisualStudio\v14.0\DotNet\Microsoft.DotNet.Props" was not found. Confirm that the path in the declaration is correct, and that the file exists on disk.

Also when closing Visual Studio and reopening it again I get the original error message

asp.net Core Solutions

Solution 1 - asp.net Core

@ClaudioNunes and @MegaTron have the correct answer. After reading that answer, I realized my .NET Core solution did not have a global.json file. I added a new solution folder and added a global.json file. Since none of my projects are nested in sub folders, I only had to remove "src" and "test" from the projects array:

{
  "projects": [],
  "sdk": {
    "version": "1.0.0-preview2-003131"
  }
}

The project now opens correctly in VS 2015 with VS 2017 RC installed.

Solution 2 - asp.net Core

A possible workaround is to add a global.json to solution and specify the sdk version to be used as in

{
  "projects": [ "src", "test" ],
  "sdk": {
    "version": "1.0.0-preview2-003131"
  }
}

Solution 3 - asp.net Core

Go to Programs and Resources, use "Core" to filter and find Preview 3 installation ("Microsoft .NET Core 1.0.1 - SDK Preview 3 (x64).") and remove it.

NOTE: Run dotnet --version before and after remove this SDK. On my case results in 1.0.0-preview3-004056(before) and 1.0.0-preview2-1-003177(after).

I can't see side effects on vs2017 yet.

Solution 4 - asp.net Core

Take a look at this link: https://github.com/aspnet/Tooling/blob/master/known-issues-vs2017.md#known-issues-for-aspnet-core-support-in-visual-studio-2017

If you update the tooling for Visual Studio 2015 to the latest version, it should fix the issue. Note this is not the Visual Studio 2015 update, but the ASP.NET Core and tooling.

Solution 5 - asp.net Core

The project upgrade has been improved from Visual Studio 2017 RC to Visual Studio 2017 RTM and is working now.

I ended up opening my Visual Studio 2015 ASP.NET Core Solution in Visual Studio 2017 which upgraded each project in the solution. I then updated the nuget packages and the solution worked without any side effects.

Content Type	Original Author	Original Content on Stackoverflow
Question	dfmetro	View Question on Stackoverflow
Solution 1 - asp.net Core	Stephen Peterson	View Answer on Stackoverflow
Solution 2 - asp.net Core	Claudio Nunes	View Answer on Stackoverflow
Solution 3 - asp.net Core	Luiz Carlos Faria	View Answer on Stackoverflow
Solution 4 - asp.net Core	Todd Miranda	View Answer on Stackoverflow
Solution 5 - asp.net Core	dfmetro	View Answer on Stackoverflow