PM> get-help entityframework
get-help : Object reference not set to an instance of an object.
At line:1 char:1
+ get-help entityframework
+ ~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [Get-Help], NullReferenceException
+ FullyQualifiedErrorId : System.NullReferenceException,Microsoft.PowerShell.Commands.GetHelpCommand
I guess it might be a problem related to PowerShell so I've listed its version number here
PM> $PSVersionTable.PSVersion
Major Minor Build Revision
----- ----- ----- --------
5 0 10586 494
And I'm using
Microsoft Visual Studio Community 2017
Version 15.8.7

Have you recently upgraded any related components? I ask because another user saw similar behaviour with NuGet after an MVC upgrade: https://github.com/NuGet/Home/issues/2192
Check that your NuGet and Entity Framework packages are up-to-date.
Are there any other strings for which get-help returns a similar error? If not, perhaps go so far as to uninstall and reinstall Entity Framework?