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ASP.NET: Handling server cached file for short-term

I have this specific scenario:
The user is sending me request which contains a URL to a file in my private repository.
The server side catch this request and Download the file.
The server making some calculation on the downloaded file.
The server sending the results back to client.
I implemented this in the "Naive" way. Which mean, I downloading the file (step 2) for each request. In most cases, the user will send the same file. So, I thought about better approach: keep the downloaded file in short term "cache".
This mean, I will download the item once, and use this for every user request.
Now the question is, how to manage those files?
In "perfect world", I will use the downloaded file for up to 30 minutes. After this time, I won't use it any more. So, optional solutions are:
Making a file system mechanism to handling files for short terms. Negative: Complex solution.
Using temporary directory to do this job (e.g. Path.GetTempFileName()). Negative: What if the system will start to delete those files, in the middle of reading it?
So, it's seems that each solution has bad sides. What do you recommend?

Asynchronous or batch processing with C#

I have a .Net application in C# that I am in need of some async processing. The user will upload a file of PEOPLE records from the aspx page and the system should upload the file, parse the file, load the people in the database, and then move the file out of the initial directory that it was uploaded to.
I don't want the user to have to wait for this, as some files may have thousands of records, and the system could take a while to go through all of them. I basically want to return a message that says, "Thank you for uploading your file. The system will process it and send you an email when it has been completed".
I have read about the new async/await keywords, but I'm not sure if that is the route that I should take for this. I basically just need a button event handler to upload the file and the kick off a "batch" process to finish dealing with the file while returning control to the user on the UI to do whatever else he/she wants to do on the site.
I guess the secondary question would be: Does await return control to the user when used within a button event handler method? If so, then this seems to be a perfect solution for me as it won't block the thread or the user.
Is there a better method or pattern that I should use for this, or is async/await sufficient?

I guess the secondary question would be: Does await return control to the user when used within a button event handler method? If so, then this seems to be a perfect solution for me as it won't block the thread or the user.
await does yield to the message loop when used within a button event handler method in a GUI application.
Is there a better method or pattern that I should use for this, or is async/await sufficient?
async/await will not do this, because async doesn't change the HTTP protocol - your await will just yield to the ASP.NET thread pool (not to the user's browser).
The best way to solve this is to have your ASP.NET page write the file to disk (asynchronously, if possible), and then return the response "we'll email you when it's done".
Then you can have a Win32 service or something that monitors that directory, processes the files, and sends emails. Note that you should use Azure Blobs/Queues instead of the file system if you plan to deploy this to the cloud.

You can use asynchronous page - based on <%# Page Async="true" ... %>
Link : http://msdn.microsoft.com/en-us/magazine/cc163725.aspx

If you're comfortable with using ASP.NET/ThreadPool to process the file parsing/database work/email notification you can implement this using an HttpModule/Timer. Use ASP.NET to upload the file and the HttpModule to either monitor file system for new uploads and process the files, or add a database record when file is uploaded and periodically poll the database for new records.
This article will get you going and also outlines the issues you may face using this method.
If you need something more complicated or your site has a lot of traffic you'd better use a separate process (windows service or scheduled task) for the batch process.
If you require any sample code I can post, but currently using .NET 3.5 rather than 4.0 at the moment.

New opened window opens but closes immediately

I'm trying to download file from FTP using javascript, for which I created the following topic:
Is it possible to download file from FTP using Javascript?
From there I learned that I can use window.open('ftp://xyz.org/file.zip'); to download the file. It opens a browser new window, but the window closes immediately.
How I can I force it to stay open?
Actually I do all these in Silverlight application:
Here is the code:
HtmlPage.Window.Eval("window.open('" + url+ "', 'Download', 'height=500,width=800,top=10,left=10');");
I also tried this,
string targetFeatures = "height=500,width=800,top=10,left=10";
HtmlPage.Window.Navigate(new Uri(url), "_blank", targetFeatures);
But both results in same : it opens a window, and closes it immediately. I see it just for fraction of second!

I know this doesn't answer your question, and I'm sure you know all of this. I'm answering more because I don't see this point brought up often. :)
Silverlight has very limited support for client interactions. Javascript is a shim that in my opinion gets overused to try and bypass things that Silverlight was architectured against. It would have been very easy for Microsoft to include FTP support in Silverlight but it was excluded for a reason.
However, Silverlight has great support for webservice interactions. So the recommended way of getting a file would be to call a webservice that would do the FTP transfer for you and then send the contents down to the Silverlight application via the webservice. Possibly even processing it on the webservice side for any business logic etc.
Like I said, I suspect your requirement is to not use a webservice (to pass the bandwith cost onto the user most likely). But it'd be interesting to know more about your business problem instead of your technical problem for the solution you've chosen.

It closes because it triggers file download. You can open two windows - one for message and one to download file, but I thiunk user will know it is downloading...

If I were you, I'd open up a page that has whatever visual/UI stuff you'd want to show the user, and either have a META tag that redirects to the download URL, or has a javascript blurb to fire off said download. That way, your window will stay open, but the download will still start automatically.

to keep it open use
var test = window.open();
test.location = 'ftp://openbsd.org.ar/pub/OpenBSD/2.0/arc/kernels/bsd.ecoff';
and to not open any window use
window.location = 'ftp://openbsd.org.ar/pub/OpenBSD/2.0/arc/kernels/bsd.ecoff';
or make a normal link

Remember that a browser is not meant to "display" (visually anyway) the FTP protocol, and not all browsers will suport it. If you want to allow the user to download something, consider using a normal http:// protocol, and opening a window normally as others have suggested.
If you really need the download to be hosted via FTP, consider your backend ingesting (and caching) the file and return it to the user via http

There is nothing to be parsed on the browser's side, hence it closes. If you want to have the page open, you'll have todo something dirty. Like creating a html (or php) page and serve the content you want the user to see, then with a hidden i-frame which will call the FTP contents.
This way your user will see the content you want them to see, and the file is being downloaded.

I had the exact same problem, Silverlight opening a new window for downloading a file would flash a blank window up briefly and it would disappear again without the file download occurring.
This seemed to happen in IE 8 (not 9 and up) and could be fixed by going into Tools->Internet Options->Security then click Custom level... (for whatever zone your site would be in) and go to Downloads->Automatic prompting for file downloads and make sure this is Enabled (I also have File download enabled below that). This Automatic prompting for file downloads setting seems to be absent from IE 9+.
Another workaround is to not open in a new window, if the target url immediately downloads a file it won't change the current window so there's no difference in UX:
HtmlPage.Window.Navigate(new Uri("\download.ashx?fileid=12345"));

Better user experience for website in asp.net MVC

I have a page that downloads a large HTML file from another domain then serve it to the user. The file is around 100k - 10MB and usually takes about 5min. What was think about doing something like this to make the user experience better.
download file
if file is not download within 10 seconds then displays a page that tells the user that the file is being downloaded
if the server completes the download in 1 second then it will serve the downloaded html
can this be done? do I need to use the async feature?
Updated question: the downloaded file is a html file

In order to provide an 'asynchronous' file download try a trick that Google is using: Create a hidden iframe and set it's source to the file you want to download. You can then still run javascript on your original page while the file is being downloaded through the iframe.

I think you should:
Return an HTML page to the user straight away, to tell them the transfer has started.
Start the download from the other domain in a separate process on your server.
Have the HTML from step 1 repeatedly reload, so you can check if the download has completed already, and possibly give an ETA or update to the user.
Return a link to the user when the initial transfer is complete.

It sounds like you need to use a waiting page that refreshes itself every so often and displays the status of your download. The download can be run on a separate thread using a System.Threading.Task, for instance.

ASP.Net Log Response to Output File

Occaisionally our office printer craps out on us in the middle of a print job, or someone just forgets to print because they get interrupted. In the good 'ole days, I built up my response using a StringBuilder and output the contents to the screen and to a log file in case we ever needed to go back and re-print.
Now I'm working with a system that makes use of all the .Net yumminess (Repeaters, page events, etc) rather than building up the HTML in code. Is there a way for me to log/archive the entire HTML response generated by the server for a particular page (e.g. hook into the Page_Render event and dump the output to a file)?
Thanks,
Sam

You can write an Http Module that plugs in at the end of the request pipeline and records the complete output.
See this example that should get you most of the way there.