So I'm using this code for view:
<form action="" method="post" enctype="multipart/form-data">
<label for="file">Filename:</label>
<input type="file" name="file" id="file" />
<input type="submit" />
</form>
This for model:
[HttpPost]
public ActionResult Index(HttpPostedFileBase file) {
if (file.ContentLength > 0) {
var fileName = Path.GetFileName(file.FileName);
var path = Path.Combine(Server.MapPath("~/App_Data/uploads"), fileName);
file.SaveAs(path);
}
return RedirectToAction("Index");
}
Works great unless the user add a file which isn't an image. How can I assure the file uploaded is an image. Thanks
In case it can helps anyone, Here is a static method for HttpPostedFileBase
that checks if a given uploaded file is an image:
public static class HttpPostedFileBaseExtensions
{
public const int ImageMinimumBytes = 512;
public static bool IsImage(this HttpPostedFileBase postedFile)
{
//-------------------------------------------
// Check the image mime types
//-------------------------------------------
if (!string.Equals(postedFile.ContentType, "image/jpg", StringComparison.OrdinalIgnoreCase) &&
!string.Equals(postedFile.ContentType, "image/jpeg", StringComparison.OrdinalIgnoreCase) &&
!string.Equals(postedFile.ContentType, "image/pjpeg", StringComparison.OrdinalIgnoreCase) &&
!string.Equals(postedFile.ContentType, "image/gif", StringComparison.OrdinalIgnoreCase) &&
!string.Equals(postedFile.ContentType, "image/x-png", StringComparison.OrdinalIgnoreCase) &&
!string.Equals(postedFile.ContentType, "image/png", StringComparison.OrdinalIgnoreCase))
{
return false;
}
//-------------------------------------------
// Check the image extension
//-------------------------------------------
var postedFileExtension = Path.GetExtension(postedFile.FileName);
if (!string.Equals(postedFileExtension , ".jpg", StringComparison.OrdinalIgnoreCase)
&& !string.Equals(postedFileExtension , ".png", StringComparison.OrdinalIgnoreCase)
&& !string.Equals(postedFileExtension , ".gif", StringComparison.OrdinalIgnoreCase)
&& !string.Equals(postedFileExtension , ".jpeg", StringComparison.OrdinalIgnoreCase))
{
return false;
}
//-------------------------------------------
// Attempt to read the file and check the first bytes
//-------------------------------------------
try
{
if (!postedFile.InputStream.CanRead)
{
return false;
}
//------------------------------------------
// Check whether the image size exceeding the limit or not
//------------------------------------------
if (postedFile.ContentLength < ImageMinimumBytes)
{
return false;
}
byte[] buffer = new byte[ImageMinimumBytes];
postedFile.InputStream.Read(buffer, 0, ImageMinimumBytes);
string content = System.Text.Encoding.UTF8.GetString(buffer);
if (Regex.IsMatch(content, @"<script|<html|<head|<title|<body|<pre|<table|<a\s+href|<img|<plaintext|<cross\-domain\-policy",
RegexOptions.IgnoreCase | RegexOptions.CultureInvariant | RegexOptions.Multiline))
{
return false;
}
}
catch (Exception)
{
return false;
}
//-------------------------------------------
// Try to instantiate new Bitmap, if .NET will throw exception
// we can assume that it's not a valid image
//-------------------------------------------
try
{
using (var bitmap = new System.Drawing.Bitmap(postedFile.InputStream))
{
}
}
catch (Exception)
{
return false;
}
finally
{
postedFile.InputStream.Position = 0;
}
return true;
}
}
Edit 2/10/2017: According to a suggested edit, added a finally statement to reset the stream, so we can use it later.