After installing SAGE SDK for .net 55

Add reference (ACCPAC.Advantage & ACCPAC.Advantage.Types); ( you can also get the ddl from GAC_MSIL - > c:\windows\assembly\GAC_MSIL from cmd prompt..)

in C#..write code

using ACCPAC.Advantage;

private ACCPAC.Advantage.Session session;
private DBLink mDBLinkCmpRW;

session = new ACCPAC.Advantage.Session();
session.Init("", "XX", "XX1000", "55A");
session.Open("ADMIN", "ADMIN", "SAMINC", DateTime.Today, 0);
mDBLinkCmpRW = session.OpenDBLink(ACCPAC.Advantage.DBLinkType.Company, ACCPAC.Advantage.DBLinkFlags.ReadWrite);

This is how you can connect to DATABASE OF ACCPAC (55a)
--
Sheryar Nizar
http://www.sheryar.net