.net文件上传时实现通过文件头确认文件类型的方法

本文实例讲述了.net文件上传时实现通过文件头确认文件类型的方法，其中 script 用来返回给页面的数据，读者还可以根据自身需要对相关部分自行修改。另外，文件头也可以自行添加定义。

主要代码如下：

AppCode/FileUpload.cs
using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Text.Regularexpressions;
using System.Web;

/// 

/// FileHeader 的摘要说明
/// 
public static class FileUpload
{
  private static string script = string.Empty;
  private static bool autonamed = true;
  private static Random ra = new Random();

  public static bool Autonamed
  {
    get
    {
      return autonamed;
    }
    set
    {
      autonamed = value;
    }
  }
  public static string script
  {
    get
    {
      return "var upload = [" + script + "];";
    }
  }
  public static Dictionary ImageHeader = new Dictionary();
  public static Dictionary FilesHeader = new Dictionary();
  
  static FileUpload()
 {
    ImageHeader.Add("gif", new byte[] { 71, 73, 70, 56, 57, 97 });
    ImageHeader.Add("bmp", new byte[] { 66, 77 });
    ImageHeader.Add("jpg", new byte[] { 255, 216, 255 });
    ImageHeader.Add("png", new byte[] { 137, 80, 78, 71, 13, 10, 26, 10, 0, 0, 0, 13, 73, 72, 68, 82 });
    FilesHeader.Add("pdf", new byte[] { 37, 80, 68, 70, 45, 49, 46, 53 });
    FilesHeader.Add("docx", new object[] { new byte[] { 80, 75, 3, 4, 20, 0, 6, 0, 8, 0, 0, 0, 33 }, new Regex(@"word/_rels/document.xml.rels", RegexOptions.IgnoreCase) });
    FilesHeader.Add("xlsx", new object[] { new byte[] { 80, 75, 3, 4, 20, 0, 6, 0, 8, 0, 0, 0, 33 }, new Regex(@"xl/_rels/workbook.xml.rels", RegexOptions.IgnoreCase) });
    FilesHeader.Add("pptx", new object[] { new byte[] { 80, 75, 3, 4, 20, 0, 6, 0, 8, 0, 0, 0, 33 }, new Regex(@"ppt/_rels/presentation.xml.rels", RegexOptions.IgnoreCase) });
    FilesHeader.Add("doc", new object[] { new byte[] { 208, 207, 17, 224, 161, 177, 26, 225 }, new Regex(@"microsoft( office)? word(?![sS]*?microsoft)", RegexOptions.IgnoreCase) });
    FilesHeader.Add("xls", new object[] { new byte[] { 208, 207, 17, 224, 161, 177, 26, 225 }, new Regex(@"microsoft( office)? excel(?![sS]*?microsoft)", RegexOptions.IgnoreCase) });
    FilesHeader.Add("ppt", new object[] { new byte[] { 208, 207, 17, 224, 161, 177, 26, 225 }, new Regex(@"c.u.r.r.e.n.t. .u.s.e.r(?![sS]*?[a-z])", RegexOptions.IgnoreCase) });
    FilesHeader.Add("avi", new byte[] { 65, 86, 73, 32 });
    FilesHeader.Add("mpg", new byte[] { 0, 0, 1, 0xBA });
    FilesHeader.Add("mpeg", new byte[] { 0, 0, 1, 0xB3 });
    FilesHeader.Add("rar", new byte[] { 82, 97, 114, 33, 26, 7 });
    FilesHeader.Add("zip", new byte[] { 80, 75, 3, 4 });
  }

  private static string DateTimeStamp()
  {
    return DateTime.Now.ToString("yyyyMMddHHmmss") + ra.Next(0, 99999).ToString("00000");
  }

  private static string FileType(Stream str)
  {
    string FileExt = string.Empty;
    foreach (string ext in FilesHeader.Keys)
    {
      byte[] header = FilesHeader[ext].GetType() == (new byte[] { }).GetType() ? (byte[])FilesHeader[ext] : (byte[])(((object[])FilesHeader[ext])[0]);
      byte[] test = new byte[header.Length];
      str.Position = 0;
      str.Read(test, 0, test.Length);
      bool same = true;
      for (int i = 0; i < test.Length; i++)
      {
 if (test[i] != header[i])
 {
   same = false;
   break;
 }
      }
      if (FilesHeader[ext].GetType() != (new byte[] { }).GetType() && same)
      {
 object[] obj = (object[])FilesHeader[ext];
 bool exists = false;
 if (obj[1].GetType().ToString() == "System.Int32")
 {
   for (int ii = 2; ii < obj.Length; ii++)
   {
     if (str.Length >= (int)obj[1])
     {
str.Position = str.Length - (int)obj[1];
byte[] more = (byte[])obj[ii];
byte[] testmore = new byte[more.Length];
str.Read(testmore, 0, testmore.Length);
if (Encoding.GetEncoding(936).GetString(more) == Encoding.GetEncoding(936).GetString(testmore))
{
  exists = true;
  break;
}
     }
   }
 }
 else if (obj[1].GetType().ToString() == "System.Text.Regularexpressions.Regex")
 {
   Regex re = (Regex)obj[1];
   str.Position = 0;
   byte[] buffer = new byte[(int)str.Length];
   str.Read(buffer, 0, buffer.Length);
   string txt = Encoding.ASCII.GetString(buffer);
   if (re.IsMatch(txt))
   {
     exists = true;
   }
 }
 if (!exists)
 {
   same = false;
 }
      }
      if (same)
      {
 FileExt = ext;
 break;
      }
    }
    return FileExt;
  }

  private static string ImageType(Stream str)
  {
    string FileExt = string.Empty;
    foreach (string ext in ImageHeader.Keys)
    {
      byte[] header = ImageHeader[ext];
      byte[] test = new byte[header.Length];
      str.Position = 0;
      str.Read(test, 0, test.Length);
      bool same = true;
      for (int i = 0; i < test.Length; i++)
      {
 if (test[i] != header[i])
 {
   same = false;
   break;
 }
      }
      if (same)
      {
 FileExt = ext;
 break;
      }
    }
    if (!string.IsNullOrEmpty(FileExt))
    {
      Encoding[] chkList = new Encoding[] { Encoding.ASCII, Encoding.UTF8, Encoding.GetEncoding(936) };
      for (int i = 0; i < chkList.Length; i++)
      {
 str.Position = 0;
 string str_test = new StreamReader(str, chkList[i]).ReadToEnd();
 if (Regex.IsMatch(str_test, @"^[^u0000-u0008u000B-u000Cu000E-u001F]*$"))
 {
   FileExt = string.Empty;
   break;
 }
      }
    }
    return FileExt;
  }

  private static void CreateFolder(string path)
  {
    string t_path = HttpContext.Current.Server.MapPath(path);
    if (!Directory.Exists(t_path))
    {
      Directory.CreateDirectory(t_path);
    }
  }

  private static string CreateFileName(string name, string ext)
  {
    string filename = "/Upload/" + DateTime.Now.ToString("yyyy/MM/dd") + "/" + ext + "/" + (autonamed ? DateTimeStamp() + "." + ext : name);
    if (File.Exists(HttpContext.Current.Server.MapPath(filename)))
    {
      return CreateFileName(name, ext);
    }
    else
    {
      return filename;
    }
  }

  private static string SaveAs(HttpPostedFile file, string Ext)
  {
    string filename = CreateFileName(file.FileName, Ext);
    CreateFolder(Regex.Match(filename, @"^[sS]*?(?=[^\/]+$)").Value);
    file.SaveAs(HttpContext.Current.Server.MapPath(filename));
    return Regex.Match(HttpContext.Current.Request.Url.ToString(), @"^[sS]*?(?=(? 0)
      {
 script += (script.Length > 0 ? "," : "") + "{filename:'" + file.FileName + "',upload:false,length:0,target:null,type:''}";
      }
    }
    else
    {
      if (Regex.IsMatch(file.ContentType, @"^image/"))
      {
 string ext = ImageType(file.InputStream);
 if (string.IsNullOrEmpty(ext))
 {
   SaveInvalid(file);
   script += (script.Length > 0 ? "," : "") + "{filename:'" + file.FileName + "',upload:false,length:" + file.ContentLength + ",target:null,type:''}";
 }
 else
 {
   string filename = SaveAs(file, ext);
   script += (script.Length > 0 ? "," : "") + "{filename:'" + file.FileName + "',upload:true,length:" + file.ContentLength + ",target:'" + filename + "',type:'" + ext + "'}";
 }
      }
      else if (Regex.IsMatch(file.ContentType, @"^text/"))
      {
      }
      else
      {
 string ext = FileType(file.InputStream);
 if (string.IsNullOrEmpty(ext))
 {
   SaveInvalid(file);
   script += (script.Length > 0 ? "," : "") + "{filename:'" + file.FileName + "',upload:false,length:" + file.ContentLength + ",target:null,type:'',header:[" + "" + "]}";
 }
 else
 {
   string filename = SaveAs(file, ext);
   script += (script.Length > 0 ? "," : "") + "{filename:'" + file.FileName + "',upload:true,length:" + file.ContentLength + ",target:'" + filename + "',type:'" + ext + "'}";
 }
      }
    }
  }
}

调用页面：

using System;
using System.Web;

public partial class _Default : System.Web.UI.Page
{
  protected void Page_Load(object sender, EventArgs e)
  {
    HttpFileCollection files = Request.Files;
    FileUpload.Clear();
    for (int i = 0; i < files.Count; i++)
    {
      FileUpload.Save(files[i]);
    }
    Response.Write(FileUpload.script);
  }
}

功能至此完成，读者还可以根据自身需要进一步作出修改与完善。