Error: The reference assemblies for .NETFramework,Version=v5.0 were not found.

Issue Description

after upgrading to .NET 5 preview 8, I couldn’t start in visual studio code project without error. stuck for days now, need some help. thank you

Environment data

dotnet --info output:

$ dotnet --info
.NET SDK (reflecting any global.json):
 Version:   5.0.100-preview.8.20417.9
 Commit:    fc62663a35

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.17763
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\5.0.100-preview.8.20417.9\

Host (useful for support):
  Version: 5.0.0-preview.8.20407.11
  Commit:  bf456654f9

.NET SDKs installed:
  2.1.202 [C:\Program Files\dotnet\sdk]
  2.1.602 [C:\Program Files\dotnet\sdk]
  2.1.701 [C:\Program Files\dotnet\sdk]
  2.1.801 [C:\Program Files\dotnet\sdk]
  2.2.100 [C:\Program Files\dotnet\sdk]
  2.2.101 [C:\Program Files\dotnet\sdk]
  2.2.202 [C:\Program Files\dotnet\sdk]
  2.2.301 [C:\Program Files\dotnet\sdk]
  2.2.401 [C:\Program Files\dotnet\sdk]
  3.0.100 [C:\Program Files\dotnet\sdk]
  3.1.101 [C:\Program Files\dotnet\sdk]
  3.1.401 [C:\Program Files\dotnet\sdk]
  5.0.100-preview.8.20417.9 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.All 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.21 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.21 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.0-preview.8.20414.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.21 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.3 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.0-preview.8.20407.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.7 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.0-preview.8.20411.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

To install additional .NET runtimes or SDKs:
  https://aka.ms/dotnet-download

VS Code version: C# Extension version:

OmniSharp log

Starting OmniSharp server at 9/3/2020, 1:21:58 AM
    Target: d:\Developer\dotnet\ScyllaTest

OmniSharp server started.
    Path: c:\Users\jeanepaul\.vscode\extensions\ms-dotnettools.csharp-1.23.1\.omnisharp\1.37.0\OmniSharp.exe
    PID: 26400

[info]: OmniSharp.Stdio.Host
        Starting OmniSharp on Windows 6.2.9200.0 (x64)
[info]: OmniSharp.Services.DotNetCliService
        DotNetPath set to dotnet
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Located 3 MSBuild instance(s)
            1: Visual Studio Build Tools 2019 16.7.30413.136 - "D:\msvisualstudio\build_tools\MSBuild\Current\Bin"
            2: Visual Studio Community 2019 16.7.30413.136 - "D:\msvisualstudio\new_msvisualstudio\MSBuild\Current\Bin"
            3: StandAlone 16.8.0 - "c:\Users\jeanepaul\.vscode\extensions\ms-dotnettools.csharp-1.23.1\.omnisharp\1.37.0\.msbuild\Current\Bin"
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Registered MSBuild instance: Visual Studio Build Tools 2019 16.7.30413.136 - "D:\msvisualstudio\build_tools\MSBuild\Current\Bin"
[info]: OmniSharp.Cake.CakeProjectSystem
        Detecting Cake files in 'd:\Developer\dotnet\ScyllaTest'.
[info]: OmniSharp.Cake.CakeProjectSystem
        Could not find any Cake files
[info]: OmniSharp.MSBuild.ProjectSystem
        No solution files found in 'd:\Developer\dotnet\ScyllaTest'
[info]: OmniSharp.MSBuild.ProjectManager
        Queue project update for 'd:\Developer\dotnet\ScyllaTest\ScyllaTest.csproj'
[info]: OmniSharp.Script.ScriptProjectSystem
        Detecting CSX files in 'd:\Developer\dotnet\ScyllaTest'.
[info]: OmniSharp.Script.ScriptProjectSystem
        Could not find any CSX files
[info]: OmniSharp.WorkspaceInitializer
        Invoking Workspace Options Provider: OmniSharp.Roslyn.CSharp.Services.CSharpFormattingWorkspaceOptionsProvider, Order: 0
[info]: OmniSharp.MSBuild.ProjectManager
        Loading project: d:\Developer\dotnet\ScyllaTest\ScyllaTest.csproj
[info]: OmniSharp.WorkspaceInitializer
        Invoking Workspace Options Provider: OmniSharp.Roslyn.CSharp.Services.RenameWorkspaceOptionsProvider, Order: 100
[info]: OmniSharp.WorkspaceInitializer
        Invoking Workspace Options Provider: OmniSharp.Roslyn.CSharp.Services.ImplementTypeWorkspaceOptionsProvider, Order: 110
[info]: OmniSharp.WorkspaceInitializer
        Invoking Workspace Options Provider: OmniSharp.Roslyn.CSharp.Services.BlockStructureWorkspaceOptionsProvider, Order: 140
[info]: OmniSharp.WorkspaceInitializer
        Configuration finished.
[info]: OmniSharp.Stdio.Host
        Omnisharp server running using Stdio at location 'd:\Developer\dotnet\ScyllaTest' on host 29472.
[fail]: OmniSharp.MSBuild.ProjectLoader
        The reference assemblies for .NETFramework,Version=v5.0 were not found. To resolve this, install the Developer Pack (SDK/Targeting Pack) for this framework version or retarget your application. You can download .NET Framework Developer Packs at https://aka.ms/msbuild/developerpacks
[warn]: OmniSharp.MSBuild.ProjectManager
        Failed to load project file 'd:\Developer\dotnet\ScyllaTest\ScyllaTest.csproj'.
d:\Developer\dotnet\ScyllaTest\ScyllaTest.csproj
D:\msvisualstudio\build_tools\MSBuild\Current\Bin\Microsoft.Common.CurrentVersion.targets(1177,5): Error: The reference assemblies for .NETFramework,Version=v5.0 were not found. To resolve this, install the Developer Pack (SDK/Targeting Pack) for this framework version or retarget your application. You can download .NET Framework Developer Packs at https://aka.ms/msbuild/developerpacks

[fail]: OmniSharp.MSBuild.ProjectManager
        Attempted to update project that is not loaded: d:\Developer\dotnet\ScyllaTest\ScyllaTest.csproj

Steps to reproduce

Expected behavior

Actual behavior

[imba-tjd]

Question: Why can’t we use the StandAlone 16.8.0?

[tolgabalci]

If I am developing in VSCode, there shouldn’t be a dependency on the version of Visual Studio.