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NuGet

NuGet is the package manager for all .NET platforms.
A NuGet package is essentially a set of DLLs, resources and a manifest that are stuffed into a a zip file with a .nupkg extension.
A repository of Nuget packages is nuget.org. As of 2019-10-11, it hosts over 172'000 packages.
There are two NuGet command line tools: dotnet.exe and nuget.exe.

Download and using nuget packages in PowerShell

I was somewhat successful trying to download nuget packages with PowerShell and then using it with a script like so: 
$packageName = 'BouncyCastle'
$version     = '1.8.9.0'          # Leave empty for latest release?

$downloadURL = "https://www.nuget.org/api/v2/package/$packageName/$version"

invoke-webRequest $downloadURL -outFile $pwd/$packageName.zip
Extracting the required DLLs from the downloaded zip file 
add-type -assembly System.IO.Compression.FileSystem
$zip = [IO.Compression.ZipFile]::OpenRead("$pwd/$packageName.zip")
[IO.Compression.ZipFileExtensions]::ExtractToFile($zip.GetEntry("lib/BouncyCastle.Crypto.dll"), "$pwd/$packageName.dll")
Later … 
add-type -path "$pwd/$packageName.dll"
…
… [Org.BouncyCastle.Math.EC.AbstractFpCurve] …

See also

C:\Program Files (x86)\Microsoft SDKs\NuGetPackages

Links

www.nuget.org

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