public ProtocolVersion Protocol {get; set;}

'Declaration
 
Public Property Protocol As ProtocolVersion

Property Value

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.

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

PgSqlConnectionStringBuilder Class
PgSqlConnectionStringBuilder Members
ProtocolVersion Property