ASP.NET 文件上传

 <p>
<label>上传图片 </label>
<asp:FileUpload ID="nfile" runat="server" />
<asp:Image runat="server" ID="upload_Image" AlternateText="图片信息未进行上传"  Width="100px" Height="100px"/>
</p>
<asp:Button ID="btn_Save" runat="server" Text="提交" CssClass="opt_sub" OnClick="btn_Save_Click" />
&nbsp;&nbsp;&nbsp;&nbsp;
<asp:Button ID="btn_reset" runat="server" Text="重置" CssClass="opt_sub" OnClick="btn_reset_Click" />

protected void btn_Save_Click1(object sender, EventArgs e)
        {
            //判断是否存在文件
            if (!nfile.HasFile)
            {
                Response.Write("<script>alter('请上传文件信息!')</script>");
                return;
            }
            //判断文件的大小
            if (nfile.FileBytes.Length > (5 * 1024 * 1024))
            {
                Response.Write("<script>alter('上传文件的大小为5M!')</script>");
                return;
            }
            //创建可以上传文件后缀名的集合
            List<string> suffixlist = new List<string>()
            {
                ".jpg",".png"
            };
            //得到文件的后缀名
            string fileName = nfile.FileName;
            //获取文件的后缀名
            string suffixName = fileName.Substring(fileName.LastIndexOf(".")).ToUpper();
            //判断当前文件夹的后缀名是否存在可以上传的后缀名集合中
            string flag = (from s in suffixlist where s.Contains(suffixName) select s).FirstOrDefault();
            //判断flag是否为NULL
            if (string.IsNullOrEmpty(flag))
            {
                //定义空值
                string outStr = string.Empty;
                //foreach循环suffixlist 后缀名集合
                suffixlist.ForEach(x =>
                {
                    if (string.IsNullOrEmpty(outStr))
                    {
                        outStr = x;
                    }
                    else
                    {
                        outStr = outStr + "," + x;
                    }
                });
                Response.Write("<script>alert('可上传的文件类型的后缀名为：" + outStr + "')</script>");
            }
            //设置随机数
            Random random = new Random();
            //产生新的文件名
            fileName = DateTime.Now.ToString("yyyyMMddhhmmss") + "_" + random.Next(0, Int32.MaxValue) + suffixlist;
            //设置保存的路径
            string filePath = "/upload" + fileName;
            //开始保存文件
            NewsModal newsModal = new NewsModal()
            {
                Title = ntitle.Value.Trim(),
                Summary = nsummary.Value.Trim(),
                Ncontent = ncontent.Value.Trim(),
                Ndate = DateTime.Now,
                Author = nauthor.Value.Trim(),
                Tid = Guid.Parse(dd_tid.SelectedIndex.ToString()),
                Nfile = filePath,
                Nid = Guid.Empty
            };
            if (newsBLL.AddNews(newsModal) > 0)
            {
                nfile.SaveAs(Server.MapPath(filePath));
                upload_Image.ImageUrl = filePath;
                Response.Redirect("news_Edit.aspx");
            }
            else
            {
                Response.Write("<script>alert('操作失败!!!')</script>");
            }
        }