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.NET Framework

*.NET Framework* is an implementation of .NET that is installed on over one billion machines. It includes
The .NET Framework 4.8 implements .NET Standard 2.0 and won't move to .NET Standard 2.1

Determine .NET Framwork version

The presence of the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full registry key indiciates that at least .NET Framework 4.5 is installed.
The exact version can then be determined from this registry key's value Release and the Windows version.
See also: https://docs.microsoft.com/en-us/dotnet/framework/migration-guide/how-to-determine-which-versions-are-installed

Version 4.6.1

.NET Framework 4.6.1 has only 43 APIs that are not supported by .NET Standard 2.0. Nevertheless, it will be allowed to reference binaries that are compiled against .NET Standard 2.0

See also

The automatic PowerShell variable $psEdition is set to Desktop if the respective PowerShell sessions uses .NET Framework.
.NET implementation differences
The Docker Container Base Image Windows Server Core

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