自己创建非托管的资源，c#内存自己管理-

  public intro()
  {
   conn=dbconnection.getconn();
   conn.open();
   cmd=new oledbcommand("select top 1 * from [intro]",conn);
   try
   {
    oledbdatareader dr=cmd.executereader();
    dr.read();
    introcontent=dr.getvalue(1).tostring();
   }
   catch
   {
    introcontent="";
   }
   finally
   {
    cmd.dispose();
    conn.close();
   }
  } 

 public void dispose()
  {
   if(conn.state==connectionstate.open)
    conn.close();
   conn.dispose();
   gc.suppressfinalize(this);
  }

}

调用是-------

using(intro it=new intro())
   {

   }