我在写一个读取ACCESS数据库的类，在网上抄到一段代码，其中用到using，但我对这个using所知甚少，请哪位详细介绍一下using的用法吧
代码如下

类文件：DataConnection.cs

其中的全部代码
using System;
using System.Data;
using System.Data.OleDb;
using System.Collections.Generic;
using System.Text;

namespace CostCal
{
    public class DataConnection
    {
        public object Get_AllRecords()
        {
            DataConnection dc = new DataConnection();
            OleDbConnectionStringBuilder connectStringBuilder = new OleDbConnectionStringBuilder();
            connectStringBuilder.DataSource = @"Record.mdb";
            connectStringBuilder.Provider = "Microsoft.Jet.OLEDB.4.0";
            using (OleDbConnection cn = new OleDbConnection(connectStringBuilder.ConnectionString))
            {
                DataSet ds = new DataSet();
                OleDbCommand cmdstr = new OleDbCommand("SELECT RecordDate, RecordType, RecordCode, RecordDetails from RecordData", cn);
                cn.Open();
                using (OleDbDataReader dr = cmdstr.ExecuteReader())
                {
                    ds.Load(dr, LoadOption.OverwriteChanges, new string[] { "RecordData" });
                    return ds.Tables["RecordData"].DefaultView; 
                }
            }
        }
    }
}