上传文件类型验证，防止伪造文件上传

//验证类
using System;    
 using System.Collections.Generic;    
 using System.Web.UI.WebControls;    
 using System.IO;    
 namespace FileValidation    
 {    
         public enum FileExtension    
         {    
                 JPG = 255216,    
                 GIF = 7173,    
                 BMP = 6677,    
                 PNG = 13780 
                 // 208207 doc
                 // 8075 docx
                 // 208207 xls
                 // 8075 xlsx
                 // 7368 mp3
                 // 4838 wma
                 // 7784 mid
                 // 255216 jpg;    
                 // 7173 gif;    
                 // 6677 bmp,    
                 // 13780 png;    
                 // 7790 exe dll,    
                 // 8297 rar    
                 // 6063 xml    
                 // 6033 html    
                 // 239187 aspx    
                 // 117115 cs    
                 // 119105 js    
                 // 210187 txt    
                 //255254 sql    
                 // 6787 swf   
                 // 8075 zip   
                 // 55122 7z   
 
         }    
         public class FileValidation    
         {    
 static bool IsAllowedExtension() static bool IsAllowedExtension(FileUpload fu, FileExtension[] fileEx)    
                 {    
                         int fileLen = fu.PostedFile.ContentLength;    
                         byte[] imgArray = new byte[fileLen];    
                         fu.PostedFile.InputStream.Read(imgArray, 0, fileLen);    
                         MemoryStream ms = new MemoryStream(imgArray);    
                         System.IO.BinaryReader br = new System.IO.BinaryReader(ms);    
                         string fileclass = "";    
                         byte buffer;    
                         try    
                         {    
                                 buffer = br.ReadByte();    
                                 fileclass = buffer.ToString();    
                                 buffer = br.ReadByte();    
                                 fileclass += buffer.ToString();    
                         }    
                         catch    
                         {    
                         }    
                         br.Close();    
                         ms.Close();    
                         foreach (FileExtension fe in fileEx)    
                         {    
                                 if (Int32.Parse(fileclass) == (int)fe)    
                                         return true;    
                         }    
                         return false;    
                 }    
         }    
 }  1 protected void Button1_Click(object sender, EventArgs e)

 2     {

 3         string filename = "";

 4         Boolean fileOK = false;

 5         if (FileUpload1.HasFile)

 6         {

 7             String fileExtension = System.IO.Path.GetExtension(FileUpload1.FileName).ToLower();

 8             String[] allowedExtensions = { ".gif", ".png", ".jpeg", ".jpg" };

 9             for (int i = 0; i < allowedExtensions.Length; i++)

             {

                 if (fileExtension == allowedExtensions[i])

                 {

                     fileOK = true;

                 }

             }

         }

 

         FileExtension[] fe = { FileExtension.BMP, FileExtension.GIF, FileExtension.JPG, FileExtension.PNG };

         if (fileOK && FileValidation.IsAllowedExtension(FileUpload1, fe))

         {

             string fileExt = System.IO.Path.GetExtension(FileUpload1.FileName).ToLower();

             filename = "Images/" + DateTime.Now.ToString("yyyyMMddHHmmss") + fileExt;

             FileUpload1.PostedFile.SaveAs(Server.MapPath(filename));

         }

         else

         {

             Response.Write("<script>alert('只支持以下格式的图片\\rJPG,BMP,GIF,PNG！');</script>");

             return;

         }

 

     }

 }