Default DotNet console project full of errors.

[RGFTheCoder]

Issue Description

Making the default dotnet new console project throws everything as an error, but running the project works fine.

Steps to Reproduce

run dotnet new console
run dotnet restore
open Program.cs

Expected Behavior

No errors are shown and itellisense works properly.

Actual Behavior

Every reference is thrown as an error and VSCode reports 26 problems.
Ex:

Logs

OmniSharp log

Starting OmniSharp server at 10/11/2020, 3:13:21 PM
    Target: /media/linx/Data/code/csharp/diploidEvo

OmniSharp server started with Mono 6.12.0 (/usr/bin/mono).
    Path: /home/linx/.vscode/extensions/ms-dotnettools.csharp-1.23.2/.omnisharp/1.37.1/omnisharp/OmniSharp.exe
    PID: 623753

[info]: OmniSharp.Stdio.Host
        Starting OmniSharp on ubuntu 20.4 (x64)
[info]: OmniSharp.Services.DotNetCliService
        DotNetPath set to dotnet
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Located 2 MSBuild instance(s)
            1: Mono 16.8.0 - "/usr/lib/mono/msbuild/Current/bin"
            2: StandAlone 16.8.0 - "/home/linx/.vscode/extensions/ms-dotnettools.csharp-1.23.2/.omnisharp/1.37.1/omnisharp/.msbuild/Current/Bin"
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Registered MSBuild instance: Mono 16.8.0 - "/usr/lib/mono/msbuild/Current/bin"
            CscToolExe = csc.exe
            CscToolPath = /home/linx/.vscode/extensions/ms-dotnettools.csharp-1.23.2/.omnisharp/1.37.1/omnisharp/.msbuild/Current/Bin/Roslyn
[info]: OmniSharp.Cake.CakeProjectSystem
        Detecting Cake files in '/media/linx/Data/code/csharp/diploidEvo'.
[info]: OmniSharp.Cake.CakeProjectSystem
        Could not find any Cake files
[info]: OmniSharp.MSBuild.ProjectSystem
        No solution files found in '/media/linx/Data/code/csharp/diploidEvo'
[info]: OmniSharp.MSBuild.ProjectManager
        Queue project update for '/media/linx/Data/code/csharp/diploidEvo/diploidEvo.csproj'
[info]: OmniSharp.Script.ScriptProjectSystem
        Detecting CSX files in '/media/linx/Data/code/csharp/diploidEvo'.
[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: /media/linx/Data/code/csharp/diploidEvo/diploidEvo.csproj
[info]: OmniSharp.WorkspaceInitializer
        Invoking Workspace Options Provider: OmniSharp.Roslyn.CSharp.Services.Completion.CompletionOptionsProvider, Order: 0
[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 '/media/linx/Data/code/csharp/diploidEvo' on host 620358.
[info]: OmniSharp.MSBuild.ProjectManager
        Successfully loaded project file '/media/linx/Data/code/csharp/diploidEvo/diploidEvo.csproj'.
[info]: OmniSharp.MSBuild.ProjectManager
        Adding project '/media/linx/Data/code/csharp/diploidEvo/diploidEvo.csproj'
[info]: OmniSharp.MSBuild.ProjectManager
        Update project: diploidEvo

C# log

Environment information

VSCode version: 1.50.0
C# Extension: 1.23.2

Mono Information

OmniSharp using global mono :6.12.0

Dotnet Information

.NET Core SDK (reflecting any global.json): Version: 3.1.402 Commit: 9b5de826fd

Runtime Environment:
OS Name: ubuntu
OS Version: 20.04
OS Platform: Linux
RID: ubuntu.20.04-x64
Base Path: /usr/share/dotnet/sdk/3.1.402/

Host (useful for support):
Version: 3.1.8
Commit: 9c1330dedd

.NET Core SDKs installed:
3.1.402 [/usr/share/dotnet/sdk]

.NET Core runtimes installed:
Microsoft.AspNetCore.App 3.1.8 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 3.1.8 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

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

Visual Studio Code Extensions

Extension	Author	Version
angelscript	renesackers	1.0.1
bash-ide-vscode	mads-hartmann	1.11.0
better-c-syntax	jeff-hykin	1.13.0
better-cpp-syntax	jeff-hykin	1.15.0
better-dockerfile-syntax	jeff-hykin	1.0.2
better-go-syntax	jeff-hykin	1.1.0
better-perl-syntax	jeff-hykin	1.0.12
better-shellscript-syntax	jeff-hykin	1.1.0
better-toml	bungcip	0.3.2
brainfuck-syntax	attilabuti	0.0.1
cmake-tools	ms-vscode	1.4.2
CobaltNext	dline	0.3.1
code-eol	jeff-hykin	1.0.11
code-runner	formulahendry	0.11.1
color-highlight	naumovs	2.3.0
CppSnippets	hars	0.0.14
cpptools	ms-vscode	1.0.1
crystal-lang	faustinoaq	0.4.0
csharp	ms-dotnettools	1.23.2
datapack-language-server	SPGoding	3.0.7
discord-vscode	icrawl	4.0.0
docomment	k--kato	0.1.18
githd	huizhou	2.2.4
gitignore	codezombiech	0.6.0
gitlens	eamodio	10.2.2
hex-hover-converter	maziac	1.0.1
hexeditor	ms-vscode	1.3.0
language-gas-x86	basdp	0.0.2
language-haskell	justusadam	3.3.0
language-mcfunction	arcensoth	0.17.0
language-pde	Tobiah	1.4.6
language-x86-64-assembly	13xforever	2.3.0
latex-utilities	tecosaur	0.3.7
latex-workshop	James-Yu	8.13.2
linkerscript	ZixuanWang	1.0.1
MagicPython	magicstack	1.1.0
markdown-all-in-one	yzhang	3.3.0
material-theme	zhuangtongfa	3.9.3
mcscript	Stevertus	0.0.3
nearley	karyfoundation	1.0.3
noctis	liviuschera	10.39.0
path-intellisense	christian-kohler	2.3.0
pdf	tomoki1207	1.1.0
polacode-2019	jeff-hykin	0.5.2
prettier-vscode	esbenp	5.7.1
project-manager	alefragnani	11.3.0
python	ms-python	2020.9.114305
quokka-vscode	WallabyJs	1.0.323
rainbow-csv	mechatroner	1.7.1
run-on-save	pucelle	1.3.1
rust	rust-lang	0.7.8
shader	slevesque	1.1.4
shaderlabformatter	litefeel	0.4.0
shell-format	foxundermoon	7.0.1
swe-starter-pack	jeff-hykin	0.0.3
Theme-MaterialKit	ms-vscode	0.1.4
todo-tree	Gruntfuggly	0.0.183
unity-code-snippets	kleber-swf	1.3.0
vsc-community-material-theme	Equinusocio	1.4.2
vsc-material-theme	Equinusocio	33.0.0
vsc-material-theme-icons	equinusocio	1.2.0
vscode-css-formatter	aeschli	1.0.1
vscode-fish	bmalehorn	1.0.20
vscode-glsllint	CADENAS	1.2.0
vscode-icon-theme	jtlowe	1.6.6
vscode-icons	vscode-icons-team	11.0.0
vscode-markdown-code-runner	jeepshen	0.1.1
vscode-npm-script	eg2	0.3.13
vscode-open-in-github	ziyasal	1.3.6
vscode-pull-request-github	GitHub	0.20.1
vscode-terminal-here	Tyriar	0.2.4
vscode-theme-onedark	akamud	2.2.2
vscode-wasm	dtsvet	1.3.1
vscode-xml	redhat	0.13.0
vshaxe	nadako	2.21.4
vsliveshare	ms-vsliveshare	1.0.2902
vsliveshare-audio	ms-vsliveshare	0.1.91
vsliveshare-pack	ms-vsliveshare	0.4.0
xd-theme	jeff-hykin	0.1.148

[RGFTheCoder]

Not using global mono seems to fix all the errors, but it shouldn't make a difference...

[filipw]

This is by design. You are using latest dotnet SDK 3.1.402 which requires msbuild 16.8 - there is no Mono released yet with that msbuild version. This is why the latest extension release switched to not use global Mono by default (it's an opt in now).

See mono/mono#20250 for the issue tracking Mono release with msbuild 16.7+

[JotaRata]

I just reverted back to C# extension v1.22.0 and it worked