如何将相对地址换成绝对地址?

小技巧:用物理路径读取access数据库
private static string Constring;
        /**//// <summary>
        /// 数据连接字符串
        /// </summary>
        public static string ConnectString
        {
            get
            {
                if(Constring==null)
                {
                    Constring=string.Format(System.Configuration.ConfigurationSettings.AppSettings["ConnectString"],
                        System.Web.HttpContext.Current.Request.PhysicalApplicationPath+(System.Configuration.ConfigurationSettings.AppSettings["DbPath"]));
                    return Constring;                }
                else
                {
                    return Constring;
                }
            }
        }参见Globals.cs <appSettings>
    <add key="ConnectString" value="Data Source={0};Password=;Provider=Microsoft.Jet.OLEDB.4.0" /> <!--数据驱动-->
        <add key="DbPath" value="DataBaseHover.mdb" /><!--物理路径-->
    </appSettings>参见web.config在调用ConnectString时始终是物理路径
D:\Hover\Hover.Web\DataBase\Hover.mdbHttpRequest.PhysicalApplicationPath 属性
获取当前正在执行的服务器应用程序的根目录的物理文件系统路径。