ODBC 

 New version:
"Driver={Microsoft ODBC for Oracle};Server=OracleServer.world;Uid=Username;Pwd=asdasd;" 

 Old version:
"Driver={Microsoft ODBC Driver for Oracle};ConnectString=OracleServer.world;Uid=myUsername;Pwd=myPassword;" 


 OLE DB, OleDbConnection (.NET) 

 Standard security:
"Provider=msdaora;Data Source=MyOracleDB;User Id=UserName;Password=asdasd;" 
This one's from Microsoft, the following are from Oracle
 Standard Security:

"Provider=OraOLEDB.Oracle;Data Source=MyOracleDB;User Id=Username;Password=asdasd;" 

 Trusted Connection:
"Provider=OraOLEDB.Oracle;Data Source=MyOracleDB;OSAuthent=1;" 


 OracleConnection (.NET) 

 Standard:
"Data Source=Oracle8i;Integrated Security=yes;" 
This one works only with Oracle 8i release  3  or later
 Specifying username and password:

"Data Source=Oracle8i;User Id=username;Password=passwd;Integrated Security=no;" 
This one works only with Oracle 8i release  3  or later
 Declare the OracleConnection:

C#:
using System.Data.OracleClient;
OracleConnection oOracleConn = new OracleConnection();
oOracleConn.ConnectionString = "my connectionstring";
oOracleConn.Open(); 

VB.NET:
Imports System.Data.OracleClient
Dim oOracleConn As OracleConnection = New OracleConnection()
oOracleConn.ConnectionString = "my connectionstring"
oOracleConn.Open() 


 Core Labs OraDirect (.NET) 

 Standard:
"User ID=scott; Password=tiger; Host=ora; Pooling=true; Min Pool Size=0;Max Pool Size=100; Connection Lifetime=0" 
Read more at Core Lab and the product page.