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Check if file is already in use by other process

I'm working on a Form application which is suppose to run on multiple machines in one network at once. There is a Form in my application (let's call it Form1) from which you can edit a XML file located on the network. In order to prevent this file from being overwritten I have to make sure that only one person at a time can access Form1.
My first try was to create an attribute inside the XML file to indicate when someone is already accessing Form1. The problem with that solution was that in the case of a sudden crash like a power outage the attribute would not be changed back to its normal value because Form1 was never properly exited. So you would have to manually change the value inside the XML file.
My current solution is running a thread inside Form1 which is constantly reading a file until Form1 is closed again. And checking if the file is already being read before allowing other people to access Form1. This solution works fine but it's not pretty since I have to have an additional file which sole purpose is to be read since I can't constantly read the XML file itself without causing other problems.
Edit: Since the first answers are the same as my current solution here is the code of my current solution.
//CODE INSIDE FORM1
//Create thread which is reading File2
Thread readerThread = new Thread(new ThreadStart(ReadFile2));
readerThread.Start();
private void ReadFile2()
{
using (FileStream stream = File.Open(pathFile2, FileMode.Open, FileAccess.Read, FileShare.None))
{
//Wait until Form1 is being closed
threadWait.WaitOne();
stream.Close();
}
}
//CODE BEFORE ACCESSING FORM1
private bool Form1OpenCheck()
{
//Check if file2 is being read
bool noAccess = false;
try
{
using (FileStream stream = File.Open(pathFile2, FileMode.Open, FileAccess.Read, FileShare.None))
{
stream.Close();
}
}
catch (IOException)
{
noAccess = true;
}
return noAccess;
}
I would appreciate it if anyone has a better solution for this problem. Thanks.

I'm using this implementation (it's not mine, props to the dude who wrote this)
/// <summary>
/// Checks if a file is ready
/// </summary>
/// <param name="sFilename"></param>
/// <returns></returns>
public static bool IsFileReady(string sFilename)
{
// If the file can be opened for exclusive access it means that the file
// is no longer locked by another process.
try
{
using (FileStream inputStream = File.Open(sFilename, FileMode.Open, FileAccess.Read, FileShare.None))
{
return inputStream.Length > 0;
}
}
catch (Exception)
{
return false;
}
}

You don't have to change the file to open it exclusively for you, just mention in your File.Open that no one may open it, not even for read-only:
string fileName = ...
using (var stream = File.Open(fileName, FileMode.Open, FileAccess.Read, FileShare.None))
{
// while here, no one else can access the file, not even delete it.
...
}
// now others can open the file again.
While you have the file open with FileShare.None, neither your process, nor another process can open the file, or access it any other way. They get an exception if they try to open or delete it. See FileShare Enum.
You or others can only open it after you Closed the Stream. Hence it is always good practice to enclose the opening in a using statement. Any exception will Close and Dispose the stream.
By the way, the overload of File.Open without a fileShare parameter also opens with FileShare.None.
So, it might be a good idea if in other use cases, you only want to read the file once, while others may still start changing it, maybe it is a good practice to open the file with FileShare.Read

Ok after talking to a colleague and a bit of brainstorming I came up with a better solution.
Inside Form1 I create a TCP Socket which is listening for connections to an IPEndPoint inside the network. Now in order to check if Form1 is already running on another machine I create another TCP Socket which is trying to connect to the same IPEndPoint. If the connection fails this means Form1 is running nowhere else and I can safely open it. If the connection works Form1 is already open somewhere and I can inform the user about it.

Need to check whether a particular text file is in open state ... if yes need to close the editor using c#

I have placed a text file in c:\my_files\test1.txt. Using C# I need to check whether the file is in an open state. If it is, I need to close the editor.
In the below code it doesn't go to the catch block if the file is in open state.
string path = #"c:\my_files\test1.txt";
FileStream stream = null;
try
{
stream = File.Open( path, FileMode.Open, FileAccess.Read, FileShare.None);
}
catch (IOException)
{
//the file is unavailable because it is:
//still being written to
//or being processed by another thread
//or does not exist (has already been processed)
//return true;
Console.WriteLine("true");
}
finally
{
if (stream != null)
stream.Close();
}

You cannot determine whether the Notepad.exe application has a file opened in memory - it does not retain an open file stream. You might be able to check that the Notepad application processes window title has the name of the file in it, but it does not have the file path, so this is extremely fragile.
Since Notepad does not have the file open, its not meaningful to attempt to close the file. You can try to close Notepad if you think the file is has copied to its memory buffer is the one you think it is ...

Out of memory crash when trying to change image?

(C#) I get an out-of-memory crash when I try setting the image of a "picture box" with one opened from a file.
My code:
string file = openImageBox.Text; // Our file
if (File.Exists(file))
{
File.Open(file, FileMode.Open); // Open the file for use.
Output.Text = "File Open Success!"; //Informing the user on how sucessful they are.
Output.ForeColor = System.Drawing.Color.Black;
Image img = Image.FromFile(file);
Display.Image = img;
}

Probably not the right answer (who knows.. it could be causing you all sorts of issues).
You don't need to "Open the file for use". This is holding a handle to the file you don't need. Just call Image.FromFile directly and it will work fine.
So remove this:
File.Open(file, FileMode.Open); // Open the file for use.
EDIT:
For completeness (and to help you learn), you need to store a reference to the stream if you want to close it. What I told you to remove above holds a handle to the file. The file is essentially open now.. until you close it.
For other code (where you're not using a method like Image.FromFile), you would either store a handle to the file so you can close it.. or use a using statement to close it for you.
Option A:
var stream = File.Open(file, FileMode.Open);
// do stuff here
stream.Close();
Option B (preferred):
using (var stream = File.Open(file, FileMode.Open)) {
// do stuff here
} // stream.Close automatically called for you

The process cannot access the file because it is being used by another process

I am getting binary data from a SQL Server database field and am creating a document locally in a directory my application has permissions. However I am still getting the error specified in the title. I have tried numerous suggestions posted on the web including those suggested in previous posts on Stackoverflow. I have also used ProcessExplorer > Find Handle to locate the lock and it returns nothing as if the file is not locked.
I am using the code below to save the file to the file system and I then try to copy this file to a new location later in the application process within another method. It is this copy method that takes the path of the newly created file that throws the exception.
The file itself is created with its content and i can open it through Windows Explorer without any problems.
Am I missing something completely obvious? Am I creating the file correctly from the database? Any help on solving or better diagnosing the problem would be much appreciated.
// Get file from DB
FileStream fs = new FileStream(
"C:\myTempDirectory\myFile.doc", FileMode.OpenOrCreate, FileAccess.Write);
BinaryWriter br = new BinaryWriter(fs);
br.Write("BinaryDataFromDB");
fs.Flush();
fs.Close();
fs.Dispose();
// Copy file
File.Copy(sourceFileName, destinationFilename, true);

Try adding a call to GC.Collect() after you have disposed of your streams to force the garbage collector to clean up.
// Get file from DB
using(FileStream fs = new FileStream("C:\myTempDirectory\myFile.doc", FileMode.OpenOrCreate, FileAccess.Write))
using(BinaryWriter br = new BinaryWriter(fs))
{
br.Write("BinaryDataFromDB");
fs.Flush();
}
//Force clean up
GC.Collect();
// Copy file
File.Copy(sourceFileName, destinationFilename, true);

change your code as follows, the problem is that the the filestream isn't being garbage collected when you need it to:
// Get file from DB
using (FileStream fs = new FileStream("C:\myTempDirectory\myFile.doc", FileMode.OpenOrCreate, FileAccess.Write))
{
BinaryWriter br = new BinaryWriter(fs);
br.Write("BinaryDataFromDB");
fs.Flush();
fs.Close();
}
// Copy file
File.Copy(sourceFileName, destinationFilename, true);

What about using?
string source = #"C:\myTempDirectory\myFile.doc";
using(FileStream fs = new FileStream(
source, FileMode.OpenOrCreate, FileAccess.Write, FileShare.Read))
{
BinaryWriter br = new BinaryWriter(fs);
br.Write("BinaryDataFromDB");
}
File.Copy(sourceFileName, destinationFilename, true);
EDIT: Try to inform a FileShare.Read permission.

I came to understand that though the error debugger says that the error lies in this code.. But that isn't where the error is..
I faced a similar issue and I came with this solution.. consider all the posts above..
May be it may help some one..
I used the Image to show it in a picturebox after retreiving from Database and saving it as "temp.bmp" using normal coding without using "using" keyword using this code at first:
PictureBox1.Image = Image.FromFile("temp.bmp");
and it raised and error and I really didn't got head and tail of the error.. and so I came up with this solution.
Instead of assigning it directly try this code:
Bitmap img;
using (Bitmap bmp = new Bitmap("temp.bmp"))
{
img = new Bitmap(bmp);
}
pictureBox1.Image = img;
coming to the filestream part I just used normal code as follows:
FileStream fs = new FileStream("filepath",FileMode.Create);
and it worked like a piece of cake
It really helped

Is it that Filestream and BinaryWriter cannot be used at the same time? For instance, a streamwriter and a streamreader cannot both be called on the same file. However, this doesn't make sense, as far as I know, it should not in this case. Perhaps try closing br as well?

Try disposing your BinaryWriter object before doing the copy.

Is there a background process such as antivirus or file-system indexing locking the file just long enough to cause problems with your application? Try pausing for 3 seconds to see if your problem disappears.
using System.Threading;
fs.Dispose();
Thread.Sleep(3000);
// Copy file

This was what I did:
Stream stream = new MemoryStream();
var tempStream = new FileStream(pathToFile, FileMode.Open);
tempStream.CopyTo(stream);
tempStream.Close();
then use stream object wherever you want.

I seem to encounter this only after I have published an application. If you close the message box and try again to debug, nothing will happen.
MS Help says to get all the way out of Visual Studio and restart it. Its easier to bring up Task manager and end the process. Its name will be the solution name followed by ".vshost" (e.g. project name: PLC.sln; process name: PLC.vshost.exe). The process will restart automatically. In Windows 7 one could usually see something happen when ending a process. But in 10 the Task Manager window rarely changes.
I get this message when I try testing a program after changing code. Apparently the .exe is not closed when one stops debugging and the error occurs when VS tries to write a newly complied exe file. I sometimes have to end the process twice to keep the error message from coming back. (I have to encounter the error twice; ending the process twice and then rerunning doesn't help.)
This is a bug in Visual Studio.

Reusing a filestream

In the past I've always used a FileStream object to write or rewrite an entire file after which I would immediately close the stream. However, now I'm working on a program in which I want to keep a FileStream open in order to allow the user to retain access to the file while they are working in between saves. ( See my previous question).
I'm using XmlSerializer to serialize my classes to a from and XML file. But now I'm keeping the FileStream open to be used to save (reserialized) my class instance later. Are there any special considerations I need to make if I'm reusing the same File Stream over and over again, versus using a new file stream? Do I need to reset the stream to the beginning between saves? If a later save is smaller in size than the previous save will the FileStream leave the remainder bytes from the old file, and thus create a corrupted file? Do I need to do something to clear the file so it will behave as if I'm writing an entirely new file each time?

Your suspicion is correct - if you reset the position of an open file stream and write content that's smaller than what's already in the file, it will leave trailing data and result in a corrupt file (depending on your definition of "corrupt", of course).
If you want to overwrite the file, you really should close the stream when you're finished with it and create a new stream when you're ready to re-save.
I notice from your linked question that you are holding the file open in order to prevent other users from writing to it at the same time. This probably wouldn't be my choice, but if you are going to do that, then I think you can "clear" the file by invoking stream.SetLength(0) between successive saves.

There are various ways to do this; if you are re-opening the file, perhaps set it to truncate:
using(var file = new FileStream(path, FileMode.Truncate)) {
// write
}
If you are overwriting the file while already open, then just trim it after writing:
file.SetLength(file.Position); // assumes we're at the new end
I would try to avoid delete/recreate, since this loses any ACLs etc.

Another option might be to use SetLength(0) to truncate the file before you start rewriting it.

Recently ran into the same requirement. In fact, previously, I used to create a new FileStream within a using statement and overwrite the previous file. Seems like the simple and effective thing to do.
using (var stream = new FileStream(path, FileMode.Create, FileAccess.Write)
{
ProtoBuf.Serializer.Serialize(stream , value);
}
However, I ran into locking issues where some other process is locking the target file. In my attempt to thwart this I retried the write several times before pushing the error up the stack.
int attempt = 0;
while (true)
{
try
{
using (var stream = new FileStream(path, FileMode.Create, FileAccess.Write)
{
ProtoBuf.Serializer.Serialize(stream , value);
}
break;
}
catch (IOException)
{
// could be locked by another process
// make up to X attempts to write the file
attempt++;
if (attempt >= X)
{
throw;
}
Thread.Sleep(100);
}
}
That seemed to work for almost everyone. Then that problem machine came along and forced me down the path of maintaining a lock on the file the entire time. So in lieu of retrying to write the file in the case it's already locked, I'm now making sure I get and hold the stream open so there are no locking issues with later writes.
int attempt = 0;
while (true)
{
try
{
_stream = new FileStream(path, FileMode.Open, FileAccess.ReadWrite, FileShare.Read);
break;
}
catch (IOException)
{
// could be locked by another process
// make up to X attempts to open the file
attempt++;
if (attempt >= X)
{
throw;
}
Thread.Sleep(100);
}
}
Now when I write the file the FileStream position must be reset to zero, as Aaronaught said. I opted to "clear" the file by calling _stream.SetLength(0). Seemed like the simplest choice. Then using our serializer of choice, Marc Gravell's protobuf-net, serialize the value to the stream.
_stream.SetLength(0);
ProtoBuf.Serializer.Serialize(_stream, value);
This works just fine most of the time and the file is completely written to the disk. However, on a few occasions I've observed the file not being immediately written to the disk. To ensure the stream is flushed and the file is completely written to disk I also needed to call _stream.Flush(true).
_stream.SetLength(0);
ProtoBuf.Serializer.Serialize(_stream, value);
_stream.Flush(true);

Based on your question I think you'd be better served closing/re-opening the underlying file. You don't seem to be doing anything other than writing the whole file. The value you can add by re-writing Open/Close/Flush/Seek will be next to 0. Concentrate on your business problem.