.NET connector for PostgreSQL

Version 1.0 is three years old. Try to use the newest one.

Npgsql is an excellent connector. Just upgrade to the new one. Make sure you take a look at the documentation it is really good. That will solve the speed issue.

You asked about an alternative, so I also have to recommend an another good connector: dotConnect for PostgreSQL. It is made by Devart. There is a simple free one as well as a fully robust pay connector. The pay one has Linq and entity framework support. http://www.devart.com/dotconnect/postgresql/