Async support for binary imports and exports (#1632).
Easier and PostgreSQL standard ways to provide client certificates for authentication (#2129).
Many other small improvements and performance optimizations have been introduced as well - you can track progress here.
Breaking changes from 4.0
.NET Framework 4.5, 4.5.1 and 4.5.2 are no longer supported. .NET Framework 4.6.1 and .NET Standard 2.0 are the lowest supported versions.
The spatial plugin, Npgsql.NetTopologySuite, has been updated to depend on NetTopologySuite 2.0.0, which is a major version introducing breaking changes. Specifically, EF Core 3.0 is the first version supporting NetTopologySuite 2.0.0; it is not possible to use EF Core 2.x with the new version of Npgsql.NetTopologySuite.
The UseSslStream property of NpgsqlConnectionStringBuilder is now marked as Obselete. SslStream is always used.
A fix was done to Npgsql's snake case naming converter (#2152); this could break code that relies on the previous conversion logic.
Contributors
Thank you very much to the following people who have contributed to the individual 4.1.x. releases.