public ProtocolVersion Protocol {get; set;}
'Declaration Public Property Protocol As ProtocolVersion
You can optionally set Protocol property to ProtocolVersion.Ver20 to force using of 2.0 version on servers that have 3.0 selected by default (PostgreSQL servers 7.4 and higher).
Note that for PostgreSQL versions lower than 7.4, you must explicitly set it to ProtocolVersion.Ver20. Otherwise, you will get an error.