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Disposing Temp Files and Deleting them

I'm using WinForms. I made a simple Image Viewer application using a picturebox to display my images. I made a way to create temporary files. These files are always picture files. When my application is done using the image i want to be able to delete these temporary on FormClosing files located at: C:\Users\taji01\AppData\Local\Temp\8bd93a0dec76473bb82a12488fd350af To do that i cannot simply call File.Delete(C://picture.jpg) because my application is still using them even though there is another picture displaying in my application. So i tried to dispose it but i couldn't figure how how to do that. Should i be using a using statement? Is there a better way to dispose and delete the file or is there a way to make this work?
_fileName = Path.Combine(Path.GetTempPath(), Guid.NewGuid().ToString("N"));
File.Copy(imagePath, _fileName);
_stream = new FileStream(_fileName, FileMode.Open, FileAccess.Read, FileOptions.DeleteOnClose);
this._Source = Image.FromStream(_stream);
Error: "The process cannot access the file C:\picture.jpg because it is being used by another process" Exeption thrown: 'System.IO.IO.Exception' in msconrlib.dll (The process cannot access the file 'C:\picture.jpg' because it is being used by another procesas")

You need to Close() your FileStream.

I think a Transaction manager will do what you want. Check out .NET Transactional File Manager. When you rollback your Transaction, it should delete your temp files automatically, as long as they were created within the Transaction scope.

Here you need to dispose the object of MailMessage.
For Ex.
// Sends email using SMTP with default network credentials
public static void SendEmailToCustomer(string To, string From, string BCC, string Subject, string Body, bool IsBodyHtml, string attachedPath = "") {
//create mail message
MailMessage message = !string.IsNullOrEmpty(From) ? new MailMessage(From, To) : new MailMessage(From, To);
//create mail client and send email
SmtpClient emailClient = new SmtpClient();
//here write your smtp details below before sending the mail.
emailClient.Send(message);
//Here you can dispose it after sending the mail
message.Dispose();
//Delete specific file after sending mail to customer
if (!string.IsNullOrEmpty(attachedPath))
DeleteAttachedFile(attachedPath);
}
//Method to delete attached file from specific path.
private static void DeleteAttachedFile(string attachedPath) {
File.SetAttributes(attachedPath, FileAttributes.Normal);
File.Delete(attachedPath);
}

Reading file after writing it

I have a strange problem. So my code follows as following.
The exe takes some data from the user
Call a web service to write(and create CSV for the data) the file at perticular network location(say \some-server\some-directory).
Although this web service is hosted at the same location where this
folder is (i.e i can also change it to be c:\some-directory). It then
returns after writing the file
the exe checks for the file to exists, if the file exists then further processing else quite with error.
The problem I am having is at step 3. When I try to read the file immediately after it has been written, I always get file not found exception(but the file there is present). I do not get this exception when I am debugging (because then I am putting a delay by debugging the code) or when Thread.Sleep(3000) before reading the file.
This is really strange because I close the StreamWriter before I return the call to exe. Now according to the documention, close should force the flush of the stream. This is also not related to the size of the file. Also I am not doing Async thread calls for writing and reading the file. They are running in same thread serially one after another(only writing is done by a web service and reading is done by exe. Still the call is serial)
I do not know, but it feels like there is some time difference between the file actually gets written on the disk and when you do Close(). However this baffling because this is not at all related to size. This happens for all file size. I have tried this with file with 10, 50, 100,200 lines of data.
Another thing which I suspected was since I was writing this file to a network location, it could be windows is optimizing the call by writing first to cache and then to network location. So I went ahead and changed the code to write it on drive(i.e use c:\some-directory), rather than network location. But it also resulted in same error.
There is no error in code(for reading and writing). As explained earlier, by putting a delay, it starts working fine. Some other useful information
The exe is .Net Framework 3.5
Windows Server 2008(64 bit, 4 GB Ram)
Edit 1
File.AppendAllText() is not correct solution, as it creates a new file, if it does not exits
Edit 2
code for writing
using (FileStream fs = new FileStream(outFileName, FileMode.Create))
{
using (StreamWriter writer = new StreamWriter(fs, Encoding.Unicode))
{
writer.WriteLine(someString)
}
}
code for reading
StreamReader rdr = new StreamReader(File.OpenRead(CsvFilePath));
string header = rdr.ReadLine();
rdr.Close();
Edit 3
used textwriter, same error
using (TextWriter writer = File.CreateText(outFileName))
{
}
Edit 3
Finally as suggested by some users, I am doing a check for the file in while loop for certain number of times before I throw the exception of file not found.
int i = 1;
while (i++ < 10)
{
bool fileExists = File.Exists(CsvFilePath);
if (!fileExists)
System.Threading.Thread.Sleep(500);
else
break;
}

So you are writing a stream to a file, then reading the file back to a stream? Do you need to write the file then post process it, or can you not just use the source stream directly?
If you need the file, I would use a loop that keeps checking if the file exists every second until it appears (or a silly amount of time has passed) - the writer would give you an error if you couldn't write the file, so you know it will turn up eventually.

Since you're writing over a network, most optimal solution would be to save your file in the local system first, then copy it to network location. This way you can avoid network connection problems. And as well have a backup in case of network failure.
Based on your update, Try this instead:
File.WriteAllText(outFileName, someString);
header = null;
using(StreamReader reader = new StreamReader(CsvFilePath)) {
header = reader.ReadLine();
}

Have you tried to read after disposing the writer FileStream?
Like this:
using (FileStream fs = new FileStream(outFileName, FileMode.Create))
{
using (StreamWriter writer = new StreamWriter(fs, Encoding.Unicode))
{
writer.WriteLine(someString)
}
}
using (StreamReader rdr = new StreamReader(File.OpenRead(CsvFilePath)))
{
string header = rdr.ReadLine();
}

View PDF in Browser in new window on button click and delete file

I am having issue with deleting file created just to send an email with attachment and then view it in browser. now i need to delete this file as this is created to just send email. how can i do this.
here is what i have got so far.
public void SendEmail()
{
EmailClient.Send(mailMessage);
//View PDF Certificate in Browser
ViewPDFinBrowser((string)fileObject);
DeleteGeneratedTempCertificateFile((string)fileObject));
}
public void ViewPDFinBrowser(string filePath)
{
PdfReader reader = new PdfReader(filePath);
MemoryStream ms = new MemoryStream();
PdfStamper stamper = new PdfStamper(reader, ms);
stamper.ViewerPreferences = PdfWriter.PageLayoutSinglePage | PdfWriter.PageModeUseThumbs;
stamper.Close();
Response.Clear();
Response.ContentType = "application/pdf";
Response.OutputStream.Write(ms.GetBuffer(), 0, ms.GetBuffer().Length);
Response.OutputStream.Close();
HttpContext.Current.ApplicationInstance.CompleteRequest();
}
public static void DeleteGeneratedTempCertificateFile(Object fileObject)
{
string filePath = (string)fileObject;
if (File.Exists(filePath))
{
File.Delete(filePath);
}
}
So here are the steps i need when i call SendEmail()
1) Sends an email with the attachment --> Temp file created
2) view the temp file in the browser
3) delete the temp file
I can understand that as long as file is in response object, i can not do anything with it because i get the error message ("File used by another process). If i close the response stream then file will be deleted but then i cant view it in browser.
i was thinking if i can manage to somehow open the file to view in browser in new window on button click, i will be able to delete the file.
OR
i am thinking i can delete the file after 10 min. as user wont be on site viewing the PDF for more then 1-2 mins.
please advice me one of the solution with example code.
appreciate your time and help.

As others have said, it's better to use the MemoryStream as-is without writing temporary files to the disk. Sometimes implementations of 3rd party components just won't allow this and in such cases after writing the binary contents of the PDF file, be sure to call close (and/or possibly dispose, always check MSDN or 3rd party API docs what the .Close() actually does) to all streams that are no longer needed. In your case close ms and reader after completing the http request.
In most cases, consider implementing the using pattern. See http://msdn.microsoft.com/en-us/library/aa664736.aspx for more details. However remember that there are caveats to this approach too, for example in WCF clients which can cause exceptions within (and thus not actually disposing all contents inside the using clause).
Also, keep in mind any concurrency issues. Keep the temporary file name random enough and consider situations where the file already exists on the local disk (i.e. fail the operation and do not send out binary to the request which the requester is not supposed to see etc).

.Net MVC Return file and then delete it

I've produced a MVC app that when you access /App/export it zips up all the files in a particular folder and then returns the zip file. The code looks something like:
public ActionResult Export() {
exporter = new Project.Exporter("/mypath/")
return File(exporter.filePath, "application/zip", exporter.fileName);
}
What I would like to do is return the file to the user and then delete it. Is there any way to set a timeout to delete the file? or hold onto the file handle so the file isn't deleted till after the request is finished?

Sorry, I do not have the code right now...
But the idea here is: just avoid creating a temporary file! You may write the zipped data directly to the response, using a MemoryStream for that.
EDIT Something on that line (it's not using MemoryStream but the idea is the same, avoiding creating a temp file, here using the DotNetZip library):
DotNetZip now can save directly to ASP.NET Response.OutputStream.

I know this thread is too old , but here is a solution if someone still faces this.
create temp file normally.
Read file into bytes array in memory by System.IO.File.ReadAllBytes().
Delete file from desk.
Return the file bytes by File(byte[] ,"application/zip" ,"SomeNAme.zip") , this is from your controller.
Code Sample here:
//Load ZipFile
var toDownload = System.IO.File.ReadAllBytes(zipFile);
//Clean Files
Directory.Delete(tmpFolder, true);
System.IO.File.Delete(zipFile);
//Return result for download
return File(toDownload,"application/zip",$"Certificates_{rs}.zip");

You could create a Stream implementation similar to FileStream, but which deletes the file when it is disposed.
There's some good code in this SO post.

download a file from server and then delete on server

ok i am downloading a file from a server and i plan to delete the file that i have downloaded on the server after it gets downloaded on the client side..
My download code is working fine but i dont know when to put the command to delete the file.
string filepath = restoredFilename.ToString();
// Create New instance of FileInfo class to get the properties of the file being downloaded
FileInfo myfile = new FileInfo(filepath);
// Checking if file exists
if (myfile.Exists)
{
// Clear the content of the response
Response.ClearContent();
// Add the file name and attachment, which will force the open/cancel/save dialog box to show, to the header
Response.AddHeader("Content-Disposition", "attachment; filename=" + myfile.Name);
//Response.AddHeader("Content-Disposition", "inline; filename=" + myfile.Name);
// Add the file size into the response header
Response.AddHeader("Content-Length", myfile.Length.ToString());
// Set the ContentType
Response.ContentType = ReturnExtension(myfile.Extension.ToLower());
//// Write the file into the response (TransmitFile is for ASP.NET 2.0. In ASP.NET 1.1 you have to use WriteFile instead)
Response.TransmitFile(myfile.FullName);
// End the response
Response.End();
}
Now i know the response.End() will stop every thing and return the value, so is there another way too do so..
I need to call a function
DeleteRestoredFileForGUI(restoredFilename);
to delete the file but dont know where to put it.. i tried putting before and after Response.End() but it does not work..
any help is appreciated... thanks

Add
Response.Flush();
DeleteRestoredFileForGUI(restoredFilename);
after the call to TransmitFile() and ditch the call to Response.End() (you don't need it).
If that does not work, then ditch TransmitFile() and go with:
Stream s = myFile.OpenRead();
int bytesRead = 0;
byte[] buffer = new byte[32 * 1024] //32k buffer
while((bytesRead = s.Read(buffer, 0, buffer.Length)) > 0 &&
Response.IsClientConnected)
{
Response.OutputStream.Write(buffer, 0, bytesRead);
Response.Flush();
}

you can't delete the file straight away as it may not have been downloaded yet. from the server side there is no easy way of telling that the file was successfully downloaded. what if an open/save dialog is opened by the browser? download won't begin until the dialog is acknowledged. (this may not be immediately and/or the dialog may be cancelled)
or, what if it is a large file and the connection is dropped before it is fully downloaded? should it be possible to attempt the download again?
the normally recommended way of dealing with your situation is to do the deletion as a separate process, after a time period which allows you to be (fairly) sure the file is no longer required and/or it can be recreated/restored if need be.
depending on your situation you could have a separate process which periodically removes/processes old files. or, if you have a low volume of traffic, you could check for and delete old files each time a new one is requested.
the identification of old files will likely be based on a file time or associated value in a darabase. either way, if there are potentially lots of files to process you are unlikely to want the overhead of checking very frequently if it is unlikely to identify a lot of files to remove.
also, be sure to way up the consequences of lots of files not being removed ASAP (is disk space really an issue?) against the side effects of possibly deleting them while still needed or creating a performance side effect by checking to zealously.

The general pattern you are following makes me wonder, are you doing this?
Create Data for Client and Save to
Disk Transmit File to Client Delete
File
If you are, you might change your system to work in memory. Since memory is managed in .Net you wouldn't have to do this manual cleanup, and depending on the size of the file this could be a good bit faster too:
Create Data for Client and Save to MemoryStream
Transmit Stream to Client

Since you set the file name in the header, you have two options:
Read the file contents into a string, delete the file, echo/print the string as the body of the message.
Rename the file something like delete-filename.xxx and then have some external process (maybe a cron job?) that goes behind and deletes any files beginning with that prefix.