这个Default.aspx如何传文件路径

这个Default.aspx怎么传文件路径
网上下了个源码,说是要Default.aspx传文件绝对路径,才开始学,看不懂,怎么传,谢谢!!

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>VIEW TIF</title>
</head>
<body>
    <form id="form1" runat="server">
    <div align="center">
        <asp:Table runat="server" ID="_tblImgs" Height="100%" Width="100%">
            <asp:TableRow>
                <asp:TableCell Width="50%"  BorderColor="Black" BorderStyle="Solid" BorderWidth="2">
                    <asp:Label runat="server" ID="_lblClickNote" Text="*Click to view bigger" Font-Size="Small"/><br />
                    <asp:PlaceHolder runat="server" ID="_plcImgsThumbs" /><br />        
                    <asp:PlaceHolder runat="server" ID="_plcImgsThumbsPager" />        
                </asp:TableCell>
                <asp:TableCell Width="50%">
                    <asp:PlaceHolder runat="server" ID="_plcBigImg" /><br />
                    <asp:HyperLink runat="server" ID="_hlRot90" Text="[Rotate Left]" Font-Underline="true" />&nbsp;
                    <asp:HyperLink runat="server" ID="_hlRot270" Text="[Rotate Right]" Font-Underline="true" />&nbsp;
                    <asp:HyperLink runat="server" ID="_hlRot180" Text="[Rotate 180]" Font-Underline="true" />&nbsp;
                    <asp:HyperLink runat="server" ID="_hlBig" Text="[Bigger]" Font-Underline="true" />&nbsp;
                    <asp:HyperLink runat="server" ID="_hlSmall" Text="[Revert]" Font-Underline="true" />&nbsp;<br />
                    <asp:Label runat="server" ID="Label1" Text="*Actions based off original page" Font-Size="Small"/><br />
                </asp:TableCell>
            </asp:TableRow>
        </asp:Table>
    </div>
    </form>
    
    <script language="javascript" type="text/javascript">
        function ChangePg(Pg) {
            Src = 'ViewImg.aspx?View=1&FilePath=' + GetBigSrc("FilePath") + "&Pg=" + Pg + "&Height=" + GetBigSrc("Height") + "&Width=" + GetBigSrc("Width");
            SrcBig = 'ViewImg.aspx?View=1&FilePath=' + GetBigSrc("FilePath") + "&Pg=" + Pg + "&Height=" + 1000 + "&Width=" + 1000;
            SrcRevert = 'ViewImg.aspx?View=1&FilePath=' + GetBigSrc("FilePath") + "&Pg=" + Pg + "&Height=" + 600 + "&Width=" + 600;
            document.getElementById('_imgBig').src = Src;
            document.getElementById('_hlRot270').onclick = function() { ChangePg(Pg); document.getElementById('_imgBig').src = Src + "&Rotate=270"; };
            document.getElementById('_hlRot180').onclick = function() { ChangePg(Pg); document.getElementById('_imgBig').src = Src + "&Rotate=180"; };