asp.net2.0上傳文件

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 System.IO;
using System.Text;
public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        //獲取文件的名稱；它與 this.FileUpload1.PostedFile.FileName所得到的值（全部路徑）是不同的，
        string filename = this.FileUpload1.FileName;
        // Response.Write(filename + this.FileUpload1.PostedFile.FileName);
        //把文件名的擴展名提取出來
        string strextension = System.IO.Path.GetExtension(filename).ToLower();
        //定義兩個數組，分別初始化各包含所有圖片和文件的擴展名
        string[] extensions ={ ".jpg", ".png", "jif", ".bmp" };
        string[] txtextensions ={ ".txt", ".doc" };
        //判斷所上傳的文件是否是文件
        for (int i = 0; i < extensions.Length; i++)
        {
            if (strextension.ToString() == extensions[i].ToString())
            {
                //判斷所上傳的文件的大小是否大於限定的值
                if (this.FileUpload1.PostedFile.ContentLength < 4096)
                {
                    this.FileUpload1.SaveAs(Server.MapPath("upload/" + filename));
                    //在image控件呈現出來
                    this.Image1.ImageUrl = "upload/" + filename;
                }
                else
                {
                    RegisterStartupScript("", "<script>alert('wrong')</script>");
                }
            }

 

        }
        //判斷所上傳的文件是否是圖片
        for (int i = 0; i < txtextensions.Length; i++)
        {

            if (strextension.ToString() == txtextensions[i].ToString())
            {
                //判斷所上傳的文件的大小是否大於限定的值
                if (this.FileUpload1.PostedFile.ContentLength < 4096)
                {
                    this.FileUpload1.SaveAs(Server.MapPath("uploadfile/" + filename));
                    this.Image1.ImageUrl = "uploadfile/" + filename;
                  
                    showFie(this.Request.MapPath("uploadfile/" + filename));
                }
                else
                {
                    RegisterStartupScript("", "<script>alert('wrong')</script>");
                }
            }
        }
    }

    //讀取文件
    public void showFie(string strFileCont)
    {
        this.ListBox1.Items.Clear();
        //得到上傳文件的名稱
        try
        {
            if (File.Exists(strFileCont))
            {
                //構件一個
                FileStream fs = new FileStream(strFileCont, FileMode.Open);
                //構件byte對象
                byte[] arr = new byte[1000];
                UTF8Encoding data = new UTF8Encoding();

                while (fs.Read(arr, 0, arr.Length) > 0)
                {
                    this.ListBox1.Items.Add(data.GetString(arr));
                }
                fs.Flush();
                fs.Close();

            }
            else
            {
                this.Response.Write("<script>alert('文件不存在')</script>");
            }
        }
        catch (Exception ex)
        {
            this.Response.Write("<script>alert('" + ex.Message + "')</script>");
        }
        finally
        {

        }
    }
}