1. Restore DB\NorthwindEF.backup to your PostgreSQL server
2. Install Npgsql driver and register DLLs to GAC (gacutil -i Mono.Security.dll; gacutil -i Npgsql.dll)
3. Edit machine.config to add a DbProviderFactories entry for Npgsql. Make sure version number and key token are correct. For example:
<add name="Npgsql Data Provider" invariant="Npgsql" description=".Net Framework Data Provider for PostgreSQL" type="Npgsql.NpgsqlFactory, Npgsql, Version=2.0.6.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7"/>
4. Edit app.config to add a Npgsql connection string. For example:
<add name="NorthwindEF (Npgsql)" connectionString="provider=Npgsql;metadata=..\..\Schemas\NorthwindEFModel.csdl|..\..\Schemas\NorthwindEFModel.msl|..\..\Schemas\NorthwindEFModel.PostgreSQL.ssdl;Provider Connection String='Server=127.0.0.1;Port=5432;Database=NorthwindEF;UserId=postgres;Timeout=1024;Password=******'" providerName="System.Data.EntityClient" />

by Frank Xia (sumast#gmail.com)