I am working on a form on a page that uses an asp:FileUpload to allow users to upload files to a server. I'm new to ASP and am using C# for my code-behind. The plan is to have the user "attach" files one at a time, adding them to an asp:listbox. Finally when the form is submitted the files in the listbox get saved to the server.
While it seems pretty easy to save files from the FileUpload by using
myFileUpload.SaveAs("path");
I am running into some difficulty figuring out how to keep track of the files independent of the FileUpload. I can get the file names really easily using
Path.GetFileName(myFileUpload.PostedFile.FileName);
but really I need to have some way of keeping track of more than just the names. My first thought was maybe to use a temporary folder of some sort, but the files are going to potentially be pretty large so I don't want to do that because saving might take a while.
How can I keep the file around so that I can save it on the server later independent of the FileUpload?
Rather than using a ListBox I would use actual <asp:FileUpload> controls so you can have access to all of the methods for that control - such as Save Etc.
You can put a bunch of these on your page and simply hide all but the first one. Then have a button to say "Add Another" - then with the click of this button show the next <asp:FileUpload> control - JQuery would be a nice choice to show the next <asp:FileUpload> that is currently hidden.
Then in your postback you can loop through all of your <asp:FileUpload> controls and if it HasFile - which is a property on the control - then perform your saving etc.
Save them into a temporary folder if needed - perhaps renaming the file with a GUID and store this list of GUID's in the users Session so you can grab those when needed.
Once you call SaveAs, you're saving the file. The base FileUpload control won't allow you to cache the file somewhere without actually uploading it to the server first. If you are looking to upload multiple files without uploading until the end, you may need to look into dynamically generating FileUpload controls (as many as the user wants). That way they can select the files to upload one at a time, then hit an "Upload" button at the end.
It's a little clunky to do it that way, though. I'd look for some third-party multiple upload controls. I've used PLUpload in the past.
Related
I currently store a number of document preview images (jpg/tif) outside of my web root. There are 100s of them, so having this work efficiently is important.
The reason they are stored outside of the web root is that they contain data the only specific users/user groups may view (but each user can have 100s of documents they can view).
My current implementation is, when the user selects ‘view image’ an ajax call is triggered and this moves the image in question to a specific folder within the web root. The location is passed back and used to display the image to the user.
When the next image is clicked, the call deletes any existing images and copies over the requested image. At session logout / timeout the users image folder is emptied.
This has a few problems, but mainly:
Files are constantly being copied and deleted
There is the risk of images being left in the folder (issues with log off scripts)
The whole time an images is in the folder it could be viewed by another users (unlikely but possible)
Is there a better way of doing this? I looked at trying to combine the BinaryReader with the ajax call (as I hoped this would cut out the need to copy the files), but can’t see how to get the data back to be used by the JS in the calling page.
Alternatively is there a way of making selected Folders only accessible to given users based on some session criteria? (I can’t imagine there is but I thought it’s worth asking.)
So if anyone has any ideas on how this can be improved that would be great.
This is a c# ASP.NET app using Jquery.
Edit:
The image is displayed using ajax, this allows for preloading and also means the rest of the page does not need to be reloaded when they select the next/previous image.
It can almost be thought of as a javascript image swapper type situation, where the images are stored outside of the web root.
Thanks.
My current implementation is, when the user selects ‘view image’ an ajax call is triggered and this moves the image in question to a specific folder within the web root.
This is horrible idea. You realize you can just access the image data and pass it to web as stream with specific mime type, right?
Maybe try to write a method that will check user credentials by cookies, if it is not OK then load and send back some standard image that will say that user must log in to view file, if it is ok then load and show proper file from a path outside of root based on url parameter (with proper headers like content-type also often referred as mime-type ofc). Then link urls to that method with proper parameter(s).
You can easily find examples of code (like here) to display image in binary form from DB. You would need just to load them from some path outside of root, not DB.
Also you don't need to load it by AJAX - just add IMG with SRC pointing to URL of handler. Or redirect / open window if it needs to be downloaded not shown.
The issue was how to get an image to show via javascript that is not in the web root.
I created a generic handler (ashx file) that based on the session values (authentication) and submitted parameters would return an image.
That in turn is being called via AJAX.
The Plan
I need to upload a file without causing a full page refresh.
The uploaded files should be stored in a temporary place (session or
cookies).
I will only save the files in the server, if the user
sucessfully fills all the form fields.
Note: This is one of the slides of a jQuery slider. So a full refresh would ruin the user experience.
The Problem
If I place a Fileuploader Control inside a AJAX Update Panel, I wont be able to acess the file on the server side.
Note:From what I have found so far, this happens due to safety reasons.
Can't be done without co-operating binaries being installed on the
client. There is no safe mechanism for an AJAX framework to read the
contents of a file and therefore be able to send it to the server. The
browser supports that only as a multipart form post from a file input
box.
The Questions
When storing the files in a temporary location, should I use session or cookies? (what if the user has cookies disabled?)
If preventing a postback, really is against the standarts of user safety. Will it harm my website reputation? (regarding SEO and such)
Which road to take?
C# ASP.Net with AJAX? (is there a workarround?)
C# ASP.Net + AJAX Control Toolkit? Does it helps? (using the AsyncFileUpload control)
C# ASP.Net + jQuery Control? (won't I have problems fetching the data from the JavaScript?)
C# ASP.Net + iFrame? (not the most elegant solution)
The total amount of cookies that you can use is limited to a few kilobytes, so that's not a viable option to store a file. So sessions would be the only remaining. Consider also to save the file in the file system and remove it if it's not going to be used, as storing files in memory (session) will limit how many users you can handle at once.
No, for functions like uploading files you don't have to worry about that. Search engines doesn't try to use such functions when scanning the page.
You can use an AJAX upload in browsers that support direct file access, but there is no way around doing a post if you need to support all browsers. However, the post doesn't have to end up loading a new page, you can put a form in an iframe, or point the target of a form to an iframe.
I want to write the entire contents of my application page (eg Mainpage.xml) to a file (in Isolated Storage ) How do I do it in WP7 ? are there any methods available to parse the page contents and write it to file in windows phone 7 ?
There is no built in way to do this.
However there are a couple of approaches you could try:
If the structure is static you could try and extract the resource containing this from the DLL. For future re-use it would be easier to load the page from the DLL again though.
If you're generating a page (or part of a page) at runtime (based on user input/preferences) and you want to be able to save/reload this then just save enough information to be able to recreate it. It's unlikely that XAML would be the best format for this though.
You could create this as you build the UI. Alternatively you could walk the visual tree to get details of all that is rendered. I'd recommend recording as you go so you can more easily keep track of non-default values in the rendered objects.
I am having the following issue, when a user fills in a form, I make an xml file based on that information and copy a file from one folder to another. (The filename is input by the user).
If the file already exists however, there will have to be a user input on whether to overwrite this file or not. I know I can't use a messagebox and if I do whether to use javascript or jQuery, I'd be adding a page as well. Preferably, I'd like to stay in C# but thats not possible without the messageboxes.
I have looked around google and stackoverflow, and the best I can think off is creating an extra page for this, where if the file exists, the user has to pick one of two options and then go back to moving the file (or not).
I am new to ASP MVC and I was wondering if this was the best way to go about it and what the best way to go is if it isn't.
Using JQuery you could make an ajax call to a controller to see if the file exists and show the user a dialog asking if they would like to overwrite the file if it exists. I can't see that you'd need a view for this at all.
I'm creating a website that is able to do multiple file uploads. However, is it possible such that when I click on the browse button and select the file to upload, it automatically adds it to a list of files to be uploaded, instead of selecting the file, and having another button to add that selected file to the list? It is something like uploadify.
Thanks.
I use Ajax Uploader for this
Latest build of Ajax Control Toolkit allows you to upload files without refreshing a page and without using addition button (not sure for multiuploading).
Also you may be interested in "[How Do I:] Multiple File Uploads in ASP.NET 2".