using System;
using System.Data;
using System.Data.SqlClient;

/// <summary>
/// Demonstrates how to work with SqlConnection objects
/// </summary>
class SqlConnectionDemo
{
    static void Main()
    {
        // 1. Instantiate the connection
        SqlConnection conn = new SqlConnection(
            "Data Source=(local);Initial Catalog=Grave Consequences;Integrated Security=SSPI");

        SqlDataReader rdr = null;

        try
        {
            // 2. Open the connection
            conn.Open();

            // 3. Pass the connection to a command object
            SqlCommand cmd = new SqlCommand("select * from Person", conn);

            //
            // 4. Use the connection
            //

            // get query results
            rdr = cmd.ExecuteReader();

            // print the CustomerID of each record
            while (rdr.Read())
            {
                Console.WriteLine(rdr[0]);
            }
        }
        finally
        {
            // close the reader
            if (rdr != null)
            {
                rdr.Close();
            }

            // 5. Close the connection
            if (conn != null)
            {
                conn.Close();
            }
        }
    }
}

using System;using System.Data.OleDb;class OleDbTest{    public static void Main()    {        //create the database connection        OleDbConnection aConnection = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=c:\\db1.mdb");        //create the command object and store the sql query        OleDbCommand aCommand = new OleDbCommand("select * from Person", aConnection);        try        {            aConnection.Open();            //create the datareader object to connect to table            OleDbDataReader aReader = aCommand.ExecuteReader();            Console.WriteLine("This is the returned data from emp_test table");            //Iterate throuth the database            while (aReader.Read())            {                Console.WriteLine(aReader.GetInt32(0).ToString());            }            //close the reader             aReader.Close();            //close the connection Its important.            aConnection.Close();        }        //Some usual exception handling        catch (OleDbException e)        {            Console.WriteLine("Error: {0}", e.Errors[0].Message);        }    }}