UPDATE : Thomas Burkhart sent me a mail telling me that this configuration syntax doesn't work on ms.net 2.0. This is the version which works: <?xml version="1.0" encoding="iso-8859-1" ?> <configuration> <system.data> <DbProviderFactories> <add name="Npgsql Data Provider" invariant="Npgsql" support="FF" description=".Net Framework Data Provider for Postgresql Server" type="Npgsql.NpgsqlFactory, Npgsql, Version=1.0.0.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7" /> </DbProviderFactories> </system.data> </configuration> Thomas said that "the tags are case sensitive and the must be outside any <applicationSettings>" Thank you Thomas for your feedback which, for sure will help others to get their configuration up and running. I will check with Mono guys to see why my original configuration worked. Hi all! Today I committed an initial support for