ADO.NET连接数据库的两种方式

//实现了IDisposable接口的类，用using括起来
//插入数据
string connString = "Data Source=(local);Initial Catalog=Linq;Integrated Security=SSPI";
using (SqlConnection conn = new SqlConnection(connString))
{
    conn.Open();
    using (SqlCommand cmd = conn.CreateCommand())
    {
        cmd.CommandText = "insert into orders (Amt,Country,City) values(240,'中国','绍兴');";
        cmd.ExecuteNonQuery();
        Console.WriteLine("插入成功");
        Console.ReadKey();
    }
}

//用SqlDataReader方式读取数据
string connString = "Data Source=(local);Initial Catalog=Linq;Integrated Security=SSPI";//用windows用户登录
using (SqlConnection conn = new SqlConnection(connString))
{
    conn.Open();
    using (SqlCommand cmd = conn.CreateCommand())
    {
        cmd.CommandText = "select * from orders";
        using (SqlDataReader reader = cmd.ExecuteReader())
        {
            while (reader.Read())
            {
                string city = reader.GetString(reader.GetOrdinal("city"));
                decimal amt = reader.GetDecimal(reader.GetOrdinal("amt"));
                Console.WriteLine(string.Format("城市：{0}, 金额：{1}", city, amt));
            }
        }
        Console.ReadKey();
    }
}

//用DataSet的方式来连接数据库
string connString = "Data Source=(local);Initial Catalog=Linq;Integrated Security=SSPI";//用windows用户登录
using (SqlConnection conn = new SqlConnection(connString))
{
    conn.Open();
    using (SqlCommand cmd = conn.CreateCommand())
    {
        cmd.CommandText = "select * from orders";
        DataSet dataset = new DataSet();
        SqlDataAdapter adapter = new SqlDataAdapter(cmd);
        /*把查询出来的结果填充到dataset中，并指定一个表面：orders
         *注意：
         *      如果不指定表名，直接用adapter.Fill(dataset)得方式填充，DataTable接收的时候根据索引号
         *      DataTable table = dataset.Tables[0];
         */
        adapter.Fill(dataset,"orders");
        DataTable table = dataset.Tables["orders"];
        for (int i = ; i < table.Rows.Count; i++)
        {
            DataRow row = table.Rows[i];
            string city = Convert.ToString(row["city"]);
            Console.WriteLine(city);
        }
        Console.ReadKey();
    }
}