public void SqlConnectionOpen()
{
SqlConnection conn= new SqlConnection();
conn.ConnectionString = "user id=sa;password=;
						initial catalog=northwind;
						connect Timeout=20";
conn.Open();
}

b. Windows 身份驗證

public void SqlConnectionOpen()
{
SqlConnection conn= new SqlConnection();
conn.ConnectionString = "Integrated Security=SSPI；
						initial catalog=northwind;
						datasource=localhost;
						connect Timeout=20";
conn.Open();
}
 

public void OleDBConnectionOpen()
{
OleDBConnection conn = new OleDbconnection();
conn.ConnectionString="Provider=Microsoft.Jet.OLEDB.4.0;
						DataSource=C:\Customer.mdb";
conn.Open();
}

conGoodDay.Open("Driver={Microsoft Access
			 	 Driver(*.mdb)};"+"Dbq=C:\a.mdb;"+
			     "Uid=Admin;"+"Pwd=;");
 

2.ODBC連線Access系統資料庫

conGoodDay.Open("Driver={Microsoft Access
        		 Driver(*.mdb)};"+"Dbq=C:\a.mdb;"+
				"SystemDB=Admin;"+"Pwd=;");

3.ODBC連線Access系統資料庫

conGoodDay.Open("Driver={Microsoft Access Driver(*.mdb)};"+"Dbq=\\server\share\a.mdb;");

4.ODBC連線Excel系統資料庫

conGoodDay.Open("Driver={Microsoft Access 				    Driver(*.xls)};"+"DriverId=790;"+
"Dbq=C:\a.xls;"+"DefaultDir=c:\somepath;");
 

5.ODBC連線Oracle系統資料庫

conGoodDay.Open("Driver={Microsoft ODBC for oracle};"+"Server=OracleServer.world;"+
"Uid=Admin;"+"Pwd=password;");

6.ODBC連線Sql Servr

conGoodDay.Open("Driver={Sql Server};"+"Server=myServer;"+"Database=myDatabaseName;"
"Uid=Admin;"+"Pwd=password;");

7.ODBC連線Visual FoxPro

conGoodDay.Open("Driver={Microsoft Visual FoxPro Driver};"+
"SourceType=DBC;"+"SourceDB=c:a.dbc;"+"Exclusive=No;");

Windows 身份驗證
建議使用 Windows 身份驗證（有時也稱為“整合安全性”）連線到支援其的資料來源。連線字串中使用的語法根據提供程式的不同而不同。下表演示用於 .NET Framework 資料提供程式的 Windows 身份驗證語法。
提供程式
語法

SqlClient 
 Integrated Security=true;
-- or --
Integrated Security=SSPI; 
 
OleDb 
 Integrated Security=SSPI; 
 
Odbc 
 Trusted_Connection=yes; 
 
OracleClient 
 Integrated Security=yes;