ASP.NETがファイルをアップロードするときのファイルタイプの高度な判断のコード

 
  
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 
  
{ 
  
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 = "     ！"; 
  
} 
  
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 = "    ！"; 
  
} 
  
else 
  
{ 
  
this.lb_info.Text = "     "; 
  
} 
  
} 
  
} 
  
catch (Exception error) 
  
{ 
  
this.lb_info.Text = "      ！  ：" + 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")//  255216 jpg;7173 gif;6677 BMP,13780 PNG;7790 exe,8297 rar 
  
{ 
  
return true; 
  
} 
  
else 
  
{ 
  
return false; 
  
} 
  
} 
  
}