服务器端检查上传文件类型(可以检测真正文件名)

后台代码：

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;public partial class _Default : System.Web.UI.Page{ //清清月儿 http://blog.csdn.net/21aspnet protected void Page_Load(object sender, EventArgs e) { } protected void bt_upload_Click(object sender, EventArgs e) { try { if (FileUpload1.PostedFile.FileName == "") { this.lb_info.Text = "请选择文件！"; } else { string filepath = FileUpload1.PostedFile.FileName; if (IsAllowedExtension(FileUpload1) == true) { string filename = filepath.Substring(filepath.LastIndexOf("//") + 1); string serverpath = Server.MapPath("images/") + filename; FileUpload1.PostedFile.SaveAs(serverpath); this.lb_info.Text = "上传成功！"; } else { this.lb_info.Text = "请上传图片"; } } } catch (Exception error) { this.lb_info.Text = "上传发生错误！原因：" + error.ToString(); } } public static bool IsAllowedExtension(FileUpload hifile) { System.IO.FileStream fs = new System.IO.FileStream(hifile.PostedFile.FileName, System.IO.FileMode.Open, System.IO.FileAccess.Read); System.IO.BinaryReader r = new System.IO.BinaryReader(fs); string fileclass = ""; byte buffer; try { buffer = r.ReadByte(); fileclass = buffer.ToString(); buffer = r.ReadByte(); fileclass += buffer.ToString(); } catch { } r.Close(); fs.Close(); if (fileclass == "255216" || fileclass == "7173")//说明255216是jpg;7173是gif;6677是BMP,13780是PNG;7790是exe,8297是rar { return true; } else { return false; } } }