windows身份驗證："server=.;database=Northwind;Integrated Security=True;"
sql驗證："server=.;database=Northwind;uid=sa;pwd=;”
也可以用如下代碼：
windows身份驗證："Data Source=.;Initial Catalog=Northwind;Integrated Security=True;"
sql驗證："Data Source=.;Initial Catalog=Northwind;User ID=sa;Password=;"