Default.aspx.cs文件代码：
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
     {
        if (Request.QueryString["id"] != null)
         {
            string contactId = new Guid(Request.QueryString["id"]).ToString();
            string pictureFilename = (Server.MapPath("/" + "productpictures"), contactId + ".jpg");
          if (File.Exists(pictureFilename))
            {
                string pictureURL = "../" + "productpictures/GetPic.aspx?id=" + contactId + "&temp=" + Guid.NewGuid().ToString();
                Image1.ImageUrl = pictureURL;
              }
         }
     }
protected void Button1_Click(object sender, EventArgs e)
{
         string contactId = new Guid(Request.QueryString["id"]).ToString();
         if (FileUpload1.HasFile)
            {
              string pictureFilename = (Server.MapPath("/" + "productpictures"), contactId + ".jpg");
              FileUpload1.SaveAs(pictureFilename);
              string pictureURL = "../" + "productpictures/GetPic.aspx?id=" + contactId + "&temp=" + Guid.NewGuid().ToString();
              Image1.ImageUrl = pictureURL;
            }
 }
}

GetPic.aspx.cs文件代码
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using

public partial class GetPic : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        string picid = Request.QueryString["id"];
        string pictureFilename = (Server.MapPath("/productpictures"), picid + ".jpg");
        Response.Clear();
        Response.ClearHeaders();
        Response.AppendHeader("content-type", "image/jpeg");
        Response.WriteFile(pictureFilename);
        Response.Flush();
        Response.End();
    }
}

问题是Default.aspx.cs中的string contactId = new Guid(Request.QueryString["id"]).ToString()不可以被替换成string contactId = Request.QueryString["id"]；而GetPic.aspx.cs中用string picid = Request.QueryString["id"]就可以，这是为什么？我没看懂。
谁能给解释一下，谢谢

Guid方法是造出唯一标识，照这个理解Default.aspx.cs中的contactId 必须唯一吧，具体代码什么意思我没看

还有个问题，这个VS2005的站点下共有4个文件，见附件，不太明白他们的作用。


解压后有：
Default.aspx
Default.aspx.cs
GetPic.aspx
GetPic.aspx.cs

主要是其中GetPic.aspx的作用

[ 本帖最后由 gege7079 于 2009-10-27 14:57 编辑 ]

的东西