上传文件高级判断

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,  
        PNG = 13780,  
        SWF = 6787,  
        RAR = 8297,  
        ZIP = 8075,  
        _7Z = 55122  
 
        // 255216 jpg;  
 
        // 7173 gif;  
 
        // 6677 bmp,  
 
        // 13780 png;  
 
        // 6787 swf  
 
        // 7790 exe dll,  
 
        // 8297 rar  
 
        // 8075 zip  
 
        // 55122 7z  
 
        // 6063 xml  
 
        // 6033 html  
 
        // 239187 aspx  
 
        // 117115 cs  
 
        // 119105 js  
 
        // 102100 txt  
 
        // 255254 sql   
 
    }  
 
    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;  
        }  
    }  
}