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Securing Temporary Files in C#

When working with an application on C# I am creating a few temporary files using the following logic:
Creating Temp File
private static string CreateTmpFile()
{
string fileName = string.Empty;
try
{
// Get the full name of the newly created Temporary file.
// Note that the GetTempFileName() method actually creates
// a 0-byte file and returns the name of the created file.
fileName = Path.GetTempFileName();
// Craete a FileInfo object to set the file's attributes
FileInfo fileInfo = new FileInfo(fileName);
// Set the Attribute property of this file to Temporary.
// Although this is not completely necessary, the .NET Framework is able
// to optimize the use of Temporary files by keeping them cached in memory.
fileInfo.Attributes = FileAttributes.Temporary;
Console.WriteLine("TEMP file created at: " + fileName);
}
catch (Exception ex)
{
Console.WriteLine("Unable to create TEMP file or set its attributes: " + ex.Message);
}
return fileName;
}
Writing to Temp File
private static void UpdateTmpFile(string tmpFile)
{
try
{
// Write to the temp file.
StreamWriter streamWriter = File.AppendText(tmpFile);
streamWriter.WriteLine("Hello from www.daveoncsharp.com!");
streamWriter.Flush();
streamWriter.Close();
Console.WriteLine("TEMP file updated.");
}
catch (Exception ex)
{
Console.WriteLine("Error writing to TEMP file: " + ex.Message);
}
}
I have also tried and followed some of the implementations found on this link for another question
and am using the following implementations in my code : Storing the file in the AppData Folder for using the ACL
However I have been asked to make sure that :
The temp files cannot be read by anyone(Not even the user) during application runtime,
And to make sure that they are deleted even when force closing the
application
For case 1: The temp files cannot be read by anyone(Not even the user) during application runtime,
How can I implement this for my application files? The temp files contain sensitive data which should not be readable even if the user themselves would like to read. Is there a way I can do that?
For case 2: To make sure that they are deleted even when force closing the
application
Here I would like to make sure than even with force close or a sudden restart the files are deleted.
If Force close: then delete the files before force close
If Restart: then delete the files on next startup
Are these doable?

how to save a file in the directory you are currently in (COSMOS)

So I'm making a Cosmos OS and I am having some trouble. I have this code that makes a file. what it does is it asks What is the name of the file and extension then what is the files contents then makes the file. The Problem is is that it only saves to main directory of 0:\ and doesn't work when you make a file while in a directory like 0:\TEST. This is the code I have for the file creator. I want to know if it's possible to make it save the file to the directory you are currently in.
Console.Write("File Name (put in the extension name):");
var finput = Console.ReadLine().ToLower();
string fileName = finput;
// Check if file already exists. If yes, delete it.
if (File.Exists(fileName))
{
File.Delete(fileName);
}
Console.Write("File Contents:\n");
var text = Console.ReadLine().ToLower();
using (FileStream fs = File.Create(fileName))
{
// Add some text to file
Byte[] title = new UTF8Encoding(true).GetBytes(text);
fs.Write(title, 0, title.Length);
}
Console.WriteLine("File Made!");

This may be a late answer, but try this:
var dir = Directory.GetCurrentDirectory;
var file = (filename);
File.Create(dir + "\\" + file);
I haven't checked this code but it should be something like this. This (should) do the same as your code above.

Xamarin Android, read a simple text file from internal storage/Download

I'm using Xamarin, and according to previous answers, this shall work:
string path = Path.Combine(Android.OS.Environment.DirectoryDownloads, "families.txt");
File.WriteAllText(path, "Write this text into a file!");
But it doesn't, I get and unhandled exception. I have set the permissions to read and write to external storage (even though this is internal).
I also tried it with this:
string content;
using (var streamReader = new StreamReader(#"file://" + path )) // with and without file://
{
content = streamReader.ReadToEnd();
}
But I got the same unhandled exception.
UPDATE: The path is the problem, since I get the else part here:
Java.IO.File file = new Java.IO.File(path);
if (file.CanRead())
testText.Text = "The file is there";
else
testText.Text = "The file is NOT there\n" + path;
Which is weird, because the path seems to be correct. The exceptions: Could not find a part of the path: /Download/families.txt
UPDATE2: On external storage, it works, with the same code... Might it be my device's problem? That would be great, cause I tested the external storage version on my friend's phone, but mine doesn't have external storage (OnePlus One), so I'm still looking for a solution (if there's any).

Finally found a solution.
var path = global::Android.OS.Environment.ExternalStorageDirectory.AbsolutePath;
var filename = Path.Combine(path.ToString(), "myfile.txt");
The path was the problem, now with a simple streamwriter it works like magic.
try
{
using (var streamWriter = new StreamWriter(filename, true))
{
streamWriter.WriteLine("I am working!");
}
}
catch { ... }

IO Exception - File being used by another process (Can't open file following directory creation)

I have got a project on the go that monitors patients for a vet while they are being operated on and writes the result to a text file. While I was experimenting with the outputting I just let the files save in the Debug folder, which worked fine. However, I've now created a full directory that creates or opens a main folder, and then a sub folder (based on input text from the program), to save the text file into.
private void createDirectory()
{ //create output file in this folder using owner name and current date
//main folder path (contains all files output from system)
string rootDirectory = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments) + "\\Horse Monitoring Records";
//sub folder path (each patient has individual subfolder)
string subDirectory = rootDirectory + "\\" + txtPatName.Text + "-" + txtOwnerName.Text;
//file name (patient has file created for each operation)
fileName = subDirectory + "\\" + txtOwnerName.Text + "-" + DateTime.Now.Date.ToString("ddMMyyyy") + ".txt";
if (!Directory.Exists(rootDirectory)) //if main folder does not exist...
{
Directory.CreateDirectory(rootDirectory); //create it in My Documents
}
if (!Directory.Exists(subDirectory)) //if patient sub folder does not exist...
{
Directory.CreateDirectory(subDirectory); //create it in Patient-Owner format
}
if (!File.Exists(fileName)) //if monitoring file does not exist...
{
File.Create(fileName); //create it in Owner-Date format
}
}
This stage works fine, but as soon as you try to save some data to the text file, it throws to a run time error stating that
The file cannot be accessed because it is being used by another process.
The exception is brought up here:
private void saveFileDetails()
{
//Once case details have been entered, create new file using these details and add data input structure
StreamWriter consoleFile = new StreamWriter(fileName);
...
}
When I went and checked out the folder, the relevant sub-folder and file had been created but the text file was blank.
I'm guessing it's something to do with closing the text file after creating the directory, which means it's already open when the system tries to open it. I can't figure out how to sort this issue out though!
The two functions shown above are called like this:
private void btnStart_Click(object sender, EventArgs e)
{
...
//file details entered upon load written to new file - according to PatID
createDirectory();
saveFileDetails();
}
Any suggestions on where to go from here would be very much appreciated!
Thanks,
Mark

The issue here is that you do
if (!File.Exists(fileName)) //if monitoring file does not exist...
{
File.Create(fileName); //create it in Owner-Date format
}
Right before you try to write to the file. Because you've just created it (if it didn't exist), chances are that the operating system hasn't released the file yet.
Like #Jauch mentioned in the comments, you could skip this check completely and use the StreamWriter overload which will create file if it doesn't exist, or append to it if it does.
private void saveFileDetails()
{
//Once case details have been entered, create new file using these details and add data input structure
using (StreamWriter consoleFile = new StreamWriter(fileName, true))
{
// ...
}
}
Alternatively you can use the following to write all of your text at once:
File.AppendAllText(textToWrite, fileName);

File.Create(fileName) returns an open stream to the file which is never closed.
To create an empty file use File.WriteAllBytes(fileName, new byte[0]);
Otherwise the 2 methods can be shortend
private void SaveFileDetails()
{
string subDirectory = Path.Combine(
Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments),
"Horse Monitoring Records");
// create the folder hierarchy if not exists. does nothing if already there
Directory.CreateDirectory(subDirectory);
// each patient has individual file
var filepath = Path.Combine(subDirectory,
txtPatName.Text + "-" + txtOwnerName.Text + "-" + DateTime.Now.Date.ToString("yyyyMMdd") + ".txt");
// creates the file if not exists
using (var writer = new StreamWriter(filepath, append: true, encoding: Encoding.UTF8))
{
// write details
}
}
Note:
merged 2 methods
.NET naming conventions applied
changed dateformat to better sort by name in explorer

StreamWriter implements IDisposable, so wrapping it in a using block can manage closing and disposing the writer and ensuring it is available the next time you want to touch that file. It can also manage creating the text file if it doesn't exist, removing the need to explicitly call File.Create.
StreamWriter consoleFile = new StreamWriter(fileName);
becomes
using (StreamWriter writer = File.AppendText("log.txt"))
{
// writing, etc.
}
or
using (StreamWriter writer = new StreamWriter(fileName, true))
{ // true says "append to file if it exists, create if it doesn't"
// writing, etc.
}
Whatever seems more readable to you will work fine.

How can I open a specific text file without using OpenFileDialog?

I have a rich text editor that I have created in C#. One of the features I am now trying to add is templates. I do not want the user to have to use an OpenFileDialog to navigate to the template and open the file. I would like to specify the filepath myself so that the user only has to click one button in order to open the template.
Currently, I am trying to achieve this using the following code:
private void formalLetterToolStripMenuItem_Click(object sender, EventArgs e)
{
try
{
FileStream fileStream = new FileStream(#".\templates\tmp1.rtf", FileMode.Open);
String str;
str = fileStream.ToString();
string fileContents = File.ReadAllText(filepath);
fileContents = fileStream.ToString();
try
{
if (richTextBoxPrintCtrl1.Modified == true);
{
NewFile();
}
richTextBoxPrintCtrl1.Rtf = fileContents;
}
catch (Exception exception)
{
MessageBox.Show("There was an error opening the template. " + exception, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
catch (Exception exception)
{
MessageBox.Show("There was an error opening the template. " + exception, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
However, whenever I try to open the template, I get an exception that is as follows:
System.ArgumentsException: File format is not valid.
However, I have tried to open the file using my OpenFileDialog and that works fine. Could somebody assist me in getting this working correctly?

Your problem is that you're trying to convert the file to a string using str = fileStream.ToString(); however, this converts the filestream to a string which is not the same thing.
Instead just do string fileContents = File.ReadAllText(filepath); to get all of the files contents into a string. You only need to use a FileStream/StreamReader if you're going to do some type of processing on the file.
Also, your use of the FileStream is a little off. I think what you really want is a StreamReader with something like this (example from msdn);
using (StreamReader sr = new StreamReader("TestFile.txt"))
{
string line;
// Read and display lines from the file until the end of
// the file is reached.
while ((line = sr.ReadLine()) != null)
{
Console.WriteLine(line);
}
}
A FileStream cannot be used to read a file. It must be passed to a StreamReader in order to actually read the file and in this case there is no point in doing that because there is an overload of the constructor which takes a filepath. It's only useful if you don't know what kind of stream the reader is going to be reading.
Where you have;
FileStream fileStream = new FileStream(#".\templates\tmp1.rtf", FileMode.Open);
String str;
str = fileStream.ToString();
string fileContents = File.ReadAllText(filepath);
fileContents = fileStream.ToString();
You actually just want thins line; string fileContents = File.ReadAllText(filepath); , nothing else. There is no need for a FileStream when you're just reading all the text into a string.

You are making very heavy weather of loading RTF. Your code to read a file into a string will never work, as #evanmcdonnal explained. Did your file dialog based code that succeeded really do it like that? Remember that a file dialog is just UI that generates a file name in a string. If your code with a file dialog works, then it will work when the file dialog is replaced with a hard coded string.
I suspect that some part of your problem is that you are using a relative path. Perhaps the working directory is not what you expect it to be. You should specify the full path to the file.
In any case, to load RTF simply call the LoadFile method of the control. But I strongly recommend passing the full path to the file.
richTextBoxPrintCtrl1.LoadFile(fullPathToRtfFile);