Support .NET 5

[amaechler]

Closes #21.

This PR attempts to address #21 as part of Hacktoberfest 🎃.

I started by added net5.0 to the list of target frameworks as suggested by @bjorkstromm. After, I ended up having to do some initial steps:

• Update the SDK used to build the project
• Optional cleanup: Removed unused usings from project
• Updated packages which also allowed me to remove some of the extra package references
• Fixed a warning when implicitly casting [] to an IEnumerable

There are still some warnings in the project, which I however believe to be out-of-scope for this PR. Specifically:

• The target framework 'netcoreapp2.1' is out of support and will not receive security updates in the future. Please refer to https://aka.ms/dotnet-core-support for more information about the support policy.
• Package 'Microsoft.Build 16.10.0' was restored using [... .NET Framrwork] instead of the project target framework '.NETCoreApp,Version=v2.1'. This package may not be fully compatible with your project.

One option to address the above would be to only support .NET 5+ forward and release an updated version with said support. Older projects could then simply use a previous version of depends until updated.

[bjorkstromm]

I think we could remove support for netcoreapp2.1 also. Do you want to send a PR for that?

[amaechler]

That was quick, thanks @bjorkstromm.

I think we could remove support for netcoreapp2.1 also.

What do you think about removing support for both netcoreapp2.1 and netcoreapp3.1? As it only changes the target of the CLI application itself, it should still be able to analyze applications that were built using .NET Core 3.

To verify this, I quickly created a new a new project and analyzed its dependencies successfully:

 # in ./somewhere
 dotnet new console -n test -f netcoreapp3.1

 # in depends
 dotnet run --project .\src\Depends --framework net5.0 -- ./somewhere/test

Am I missing something, or does that make sense?

[bjorkstromm]

@amaechler the built framework does not decide what kind of project depends can analyze. It's using MSBuild behind the scenes. The built framework however must be installed on the machine for running the depends. netcoreapp3.1 is LTS so we'd like to support that (in case user doesn't have net5.0 installed). net5.0 is current, so we like to support that as well. In a couple of weeks when net6.0 is released (will be LTS), we'd like to support that as well.

[amaechler]

Ok, that makes sense. Thanks for clarifying.