What I'm receiving
Could not install package 'Npgsql.EntityFrameworkCore.PostgreSQL 2.0.1'. You are trying to install this package into a project that targets '.NETFramework,Version=v4.5.1', but the package does not contain any assembly references or content files that are compatible with that framework.
What am I overlooking?
Version 2.0.x of Entity Framework Core is only supported by.NET Standard 2.0, which is supported by.NET Framework 4.6.1 and above, if you're searching for it (or .NET Core).
Use the package EntityFramework6.Npgsql as previously advised if you're searching for Entity Framework 6.x.