ASP.NET code for advanced judgment of file types when uploading files
- 2020-05-07 19:28:28
- OfStack
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 = " Please select file! ";
}
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 = " Upload successful! ";
}
else
{
this.lb_info.Text = " Please upload pictures ";
}
}
}
catch (Exception error)
{
this.lb_info.Text = " Error uploading! The reason: " + 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")// instructions 255216 is jpg;7173 is gif;6677 is BMP,13780 is PNG;7790 is exe,8297 is rar
{
return true;
}
else
{
return false;
}
}
}
Test passed...