Add support for pure .net 5.0

[mikeblakeuk]

In DevOps:

pool:
  vmImage: windows-latest

dotnet info #contains 3.1 and 5.0
install just dotnet 5.0
dotnet info #contains only 5.0

cproj contains:

    <Exec EnvironmentVariables="SwaggerGeneration=True" Command="dotnet swagger tofile --output $(OpenApiPath) $(TargetPath) 1.0" />

then ruining swagger gives

Tool 'swashbuckle.aspnetcore.cli' (version '5.6.3') was restored. Available commands: swagger
  
  Restore was successful.
  It was not possible to find any compatible framework version
  The framework 'Microsoft.AspNetCore.App', version '3.0.0' was not found.
    - The following frameworks were found:
        5.0.0 at [C:\hostedtoolcache\windows\dotnet\shared\Microsoft.AspNetCore.App]
  
  You can resolve the problem by installing the specified framework and/or SDK.

tools has

{
  "version": 1,
  "isRoot": true,
  "tools": {
    "swashbuckle.aspnetcore.cli": {
      "version": "5.6.3",
      "commands": [
        "swagger"
      ]
    }
  }
}
```json

[mikeblakeuk]

(note; warning NETSDK1138: The target framework 'netcoreapp3.0' is out of support and will not receive security updates in the future.)

[domaindrivendev]

I believe this may be resolved with latest master. Could you try pulling down the preview Nuget from myget.org and let me know if it works?

[mikeblakeuk]

It's warning in the CI
https://ci.appveyor.com/project/domaindrivendev/ahoy/branch/master

[domaindrivendev]

I’m aware of the warning but your original post shows an issue - does this still occur with the latest preview build

[mikeblakeuk]

The issue has gone away but only because the DevOps Agents now come with 3.1 AND 5.0 by default.
I will try and only install 5.0 later

[domaindrivendev]

Closing due to inactivity

[mikeblakeuk]

Looks like https://github.com/MicrosoftDocs/azure-devops-docs/issues/9690 is now fixed so not a problem