SqlConnection object is like a c# object.The object declare like that: SqlConnection conn = new SqlConnection( "Data Source=(local);Initial Catalog=Northwind;Integrated Security=SSPI"); This argument is called a connection string. It is define as: Data Source: Identifies the server. Integrated Security: Set to SSPI to make connection with user's Windows login User ID: Name of user configured in SQL Server. Password: Password matching SQL Server User ID. Using a SqlConnetion the connection creates as: 1.Instantiate the SqlConnection. 2.Open the connection. 3.Pass the connection to other ADO.NET objects. 4.Perform database operations with the other ADO.NET objects. 5.Close the connection.