OmniSharp.MSBuild.ProjectManager Support to .NET 5

[mauriliofilho]

Environment data

SDK do .NET Core (refletindo qualquer global.json):
Version: 5.0.100-preview.3.20161.4
Commit: dfe6198dc5

Ambiente de runtime:
OS Name: Windows
OS Version: 10.0.18363
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\5.0.100-preview.3.20161.4\

Host (useful for support):
Version: 5.0.0-preview.2.20155.1
Commit: e2881ae96b

.NET Core SDKs installed:
2.1.804 [C:\Program Files\dotnet\sdk]
2.2.402 [C:\Program Files\dotnet\sdk]
3.1.101 [C:\Program Files\dotnet\sdk]
3.1.102 [C:\Program Files\dotnet\sdk]
5.0.100-preview.3.20161.4 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed:
Microsoft.AspNetCore.All 2.1.15 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.All 2.1.16 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.All 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.1.15 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 2.1.16 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 2.2.7 [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 3.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.0-preview.3.20156.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.1.15 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.1.16 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.2.7 [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 3.1.2 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.0-preview.2.20155.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.1.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 3.1.2 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 5.0.0-preview.3.20161.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

VS Code version:

1.44.0 Insider

C# Extension version:

1.21.13

Steps to reproduce

Install SDK of .NET 5 preview on
.NET 5 PReview
run dotnet new mvc -n MyApp
genarate app with verssion default dotnet .Net 5 Preview, see in file genarate .csproj targetframework netcoreapp5.

run cd/dir MyApp

run code-insider .
(Already C# Extenssion installed)

Expected behavior

Loaded .csproj correctly

Actual behavior

receiving messa on console Failed to load project file 'c:\Users\username\MyApp01\MyApp2\MyApp.csproj'.

Seeing message to install .NET Core 3.1 or older

[filipw]

we need to update MsBuild 16.5, it's the minimum for .NET 5