At the moment i get file extension of the file like :
string fileExt = System.IO.Path.GetExtension(filUpload.FileName);
But if the user change the file extension of the file ( for example user could rename "test.txt" to "test.jpg" ), I can't get the real extension . What's the solution ?
You seem to be asking if you can identify file-type from its content.
Most solutions will indeed attempt the file extension, but there are too many different possible file types to be reliably identifiable.
Most approaches use the first several bytes of the file to determine what they are.
Here is one list, here another.
If you are only worried about text vs binary, see this SO question and answers.
See this SO answer for checking if a file is a JPG - this approach can be extended to use other file headers as in the first two links in this answer.
Whatever the user renames the file extension to, that is the real file extension.
You should never depend on the file extension to tell you what's in the file, since it can be renamed.
See "how can we check file types before uploading them in asp.net?"
There's no way to get the 'real' file extension - the file extension that you get from the filename is the real one. If file content is your concern, you can retrieve the content type using the .ContentType property and verify that it is a content type that you are expecting - eg. image/jpg.
Related
We have a windows forms legacy asp.net site that uses the AjaxFileUpload control to manage file uploads. One of our issues is that we have different file type uploads but these types are distinguished not by the extension, but by an element right before the extnsion, EG: .gh.zip vs. .gy.zip. It seems that if I add one of these, but not the other, to the AllowedFileTypes, it doesn't allow either. Is it possible to piggyback some additional JS validation code to prevent an invalid file name, or would I need to replace the entire module with something else, and if so, what would be the recommendation for something that's going to be the least time-consuming that will offer a reasonable amount of configuratability?
That control is open source - you can download the source and change it if you wish.
However, why would not just specifying zip as allowed file type work?
If I set a allowed extension of zip?
Then all of these work:
.gh.zip ok
.gy.zip ok
.pdf no
However, my markup is this:
<ajaxToolkit:AjaxFileUpload ID="AjaxFileUpload1" runat="server"
OnClientUploadCompleteAll="MyCompleteAll" ChunkSize="16384"
AllowedFileTypes="zip"
/>
So, above only allows zip files.
if I try to say add a pdf file to above que, then I get this:
So just add allowed extension type = zip
(Edit: do NOT include the "." in this extension)
I not sure why that would not work?
But as noted, you can grab the source - it is open source code now.
However, I suspect perhaps some other issue is going on here?
Or maybe you need "more" complex file extensions parsing?
I mean, you could for the "rare" cases or say some "out liner" cases allow that file up-load, and THEN the post-processing code could reject the file type anyway, right?
However, looking at above, just specify file type = zip, and you should be ok.
I have this .jpg file that cannot be opened nor viewed. But the thing is my friend who sent me this file said that this file actually contains hidden files inside and is MOST likely encrypted. I searched on Google and I found out that I had to rename the extension ".jpg" to ".zip" and tried to extract the file but it doesn't work. I forgot the message that was shown during my attempt to extract. Maybe the file is actually not a .jpg but something else and is corrupt or maybe it has "hidden" files inside.
So I'm wondering if you guys could help me out.
You should use TrIDNet http://mark0.net/soft-tridnet-e.html. I didn't test it but I think that you seek for something like this. Your file has an unknown type and you must find with which known type it matches.
I have a QDialogBox where there is an option to upload a file.
I can upload files and save them to a folder. It works fine.
But if in case there is a file that already exists in the folder, I am not sure how to handle that scenario.
I want to warn the user that the file with same name already exists.
Is there a Windows API that I can use in this case? (because when we manually save an existing file, we get a warning, how can I use that?)
If someone can point me to that documentation, it will be great.
If you are using a QFileDialog, confirmOverwrite is activated by default, so, if getSaveFileName() returned a non-empty QString, then that means the user accepted to overwrite the file. Other way, you get an empty QString.
Then, you can check if the file exists, and remove it in that case, but you know that the user was Ok with that.
There is always a potential race condition when saving files. Checking to see if the file exists first is not safe, because some other process could create a file with the same name in between the check and when you actually write the file.
To avoid problems, the file must be opened with exclusive access, and in such a way that it immediately fails if it already exists.
If you want to do things properly, take a look at these two answers:
How do I create a file in python without overwriting an existing
file
Safely create a file if and only if it does not exist with
python
You can use QDir::entryList() to get the file names in a directory if you're not using a QFileDialog.
QDir dir("/path/to/directory");
QStringList fileNames = dir.entryList();
Then iterating through file names, you can see if there's a file with the same name. If you need it, I can give an example for that too. It'd be C++, but easily adaptable to Python.
Edit: Smasho just suggested that using QDir::exists() method. You can check if the file name exists in the directory with this method instead of iterating like I suggested.
if(dir.exists(uploadedFileName))
I am using file upload mechanism to upload file for an employee and converting it into byte[] and passing it to varBinary(Max) to store into database.
Now I what I have to do is, if any file is already uploaded for employee, simply read it from table and show file name. I have only one column to store a file and which is of type VarBinary.
Is it possible to get all file information from VarBinary field?
Any other way around, please let me know.
If you're not storing the filename, you can't retrieve it.
(Unless the file itself contains its filename in which case you'd need to parse the blob's contents.)
If the name of the file (and any other data about the file that's not part of the file's byte data) needs to be used later, then you need to save that data as well. I'd recommend adding a column for the file name, perhaps one for its type (mime type or something like that for properly sending it back to the client's browser, etc.) and maybe even one for size so you don't have to calculate that on the fly for each file (useful when displaying a grid of files and not wanting to touch the large blob field in the query that populates the grid).
Try to stay away from using the file name for system-internal identity purposes. It's fine for allowing the users to search for a file by name, select it, etc. But when actually making the request to the server to display the file it's better to use a simple integer primary key from the table to actually identify it. (On a side note, it's probably a good idea to put a unique constraint on the file name column.)
If you also need help displaying the file to the user, you'll probably want to take the approach that's tried and true for displaying images from a database. Basically it involves having a resource (generally an .aspx page, but could just as well be an HttpHandler instead) which accepts the file ID as a query string parameter and outputs the file.
This resource would have no UI (remove everything from the .aspx except the Page directive) and would manually manipulate the response headers (this is where you'd set the content type from the file's type), write the byte stream to the client, and end the response. From the client's perspective, something like ~/MyContent/MyFile.aspx?fileID=123 would be the file. (You can suggest a file name to the browser for saving purposes in the response headers, which you'd probably want to do with the file's stored name.)
There's no shortage of quick tutorials (some several years old, it's been around for a while) on how to do this with images. Just remember that there's essentially no difference from the server's perspective if it's an image or any other kind of file. All the server needs to do is send the type in the response headers and write the file's bytes to the client. How the client handles the file is up to the browser. In the vast majority of cases, the browser will know what to do (display an image, display via a plugin a PDF, save a .doc, etc.).
I've got a web page with a link, and the link is suppose to correspond to a PDF is the given user's language. I'm wondering where I should put these PDF files though. If I put them in App_LocalResources, I can't specify a link to /App_LocalResources/TOS_en-US.pdf can I?
The PDF should definitely not be in the App_LocalResources folder. That folder is only for RESX files.
The PDF files can go anywhere else in your app. For example, a great place to put them would be in a ~/PDF folder. Then your links will have to be dynamically generated (similar to what Greg has shown):
string cultureSpecificFileName = String.Format("TOS_{0}.pdf", CultureInfo.CurrentCulture.Name);
However, there are some other things to consider:
You need a way to ensure that you actually have a PDF for the given language. If someone shows up at your site and has their culture specified as Klingon, it's unlikely that you have such a PDF.
You need to decide exactly what the file format will be. In the example given, the file would have to be named TOS_en-US.pdf. It you want to use the 2-letter ISO culture names, use CurrentCulture.TwoLetterISOLanguageName and then the file name would be TOS_en.pdf.
I would store the filename somewhere with an argument in it (i.e. "TOS_{0}.pdf" ) and then just add the appropriate suffix in code:
string cultureSpecificFileName = string.Format("TOS_{0}.pdf", CultureInfo.CurrentCulture);
Does the PDF have to have the same file name for each of the different languages? If not, put them all into a directory and just store the path in your resources file.