.net上传文件时获取文件的真实类型

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.IO;

public partial class niunantest : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

}

protected void Button1_Click(object sender, EventArgs e)

{

string str = FileUpload1.PostedFile.ContentType;

Response.Write("文件类型："+str);

string filename = "";

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

if (FileValidation.IsAllowedExtension(FileUpload1, fe))

{

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

Response.Write("<br>验证通过！");

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

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

}

else

{

Response.Write( "<br>验证不通过，只支持以下格式的图片：JPG,GIF,PNG");

return;

}

}

public enum FileExtension

{

JPG = 255216,

GIF = 7173,

BMP = 6677,

PNG = 13780,

RAR = 8297,

jpg = 255216,

exe = 7790,

xml = 6063,

html = 6033,

aspx = 239187,

cs = 117115,

js = 119105,

txt = 210187,

sql = 255254

}

public class FileValidation

{

public 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;

}

}

}