请问在VC中使用ADO时如何设置Provider的值？

Question

pConn->Open("Provider=sqloledb;Data Source=Server1;"
         "Initial Catalog=test1;User Id=sa;Password=sa;",
         "", "", adConnectUnspecified);
pConn->Open("Driver={Microsoft dBASE Driver (*.dbf)};DBQ=C:\\tmp\\; DriverID=533;"
,"","",adConnectUnspecified);
pConn->Open("PROVIDER=MSDASQL;DRIVER={Microsoft Access Driver (*.mdb)};DBQ=C:\\tmp\\test.mdb;UID=;PWD=aaa;" //pConn->Open("Provider= Microsoft.Jet.OLEDB.4.0;Data Source=C:\\tmp\\test.mdb;"//this is also OK
,"","",adConnectUnspecified);