levi levi - 25 days ago 7
C# Question

Wait Until File Is Completely Written

When a file is created (

FileSystemWatcher_Created
) in one directory I copy it to another. But When I create a big (>10MB) file it fails to copy the file, because it starts copying already, when the file is not yet finished creating...

This causes Cannot copy the file, because it's used by another process to be raised. ;(

Any help?

class Program
{
static void Main(string[] args)
{
string path = @"D:\levan\FolderListenerTest\ListenedFolder";
FileSystemWatcher listener;
listener = new FileSystemWatcher(path);
listener.Created += new FileSystemEventHandler(listener_Created);
listener.EnableRaisingEvents = true;

while (Console.ReadLine() != "exit") ;
}

public static void listener_Created(object sender, FileSystemEventArgs e)
{
Console.WriteLine
(
"File Created:\n"
+ "ChangeType: " + e.ChangeType
+ "\nName: " + e.Name
+ "\nFullPath: " + e.FullPath
);
File.Copy(e.FullPath, @"D:\levan\FolderListenerTest\CopiedFilesFolder\" + e.Name);
Console.Read();
}
}

Answer

There is only workaround for the issue you are facing.

Check whether file id in process before starting the process of copy. You can call the following function until you get the False value.

1st Method:

private bool IsFileLocked(FileInfo file)
{
    FileStream stream = null;

    try
    {
        stream = file.Open(FileMode.Open, FileAccess.ReadWrite, 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;
    }
    finally
    {
        if (stream != null)
            stream.Close();
    }

    //file is not locked
    return false;
}

2nd Method:

const int ERROR_SHARING_VIOLATION = 32;
const int ERROR_LOCK_VIOLATION = 33;
private bool IsFileLocked(string file)
{
    //check that problem is not in destination file
    if (File.Exists(file) == true)
    {
        FileStream stream = null;
        try
        {
            stream = File.Open(file, FileMode.Open, FileAccess.ReadWrite, FileShare.None);
        }
        catch (Exception ex2)
        {
            //_log.WriteLog(ex2, "Error in checking whether file is locked " + file);
            int errorCode = Marshal.GetHRForException(ex2) & ((1 << 16) - 1);
            if ((ex2 is IOException) && (errorCode == ERROR_SHARING_VIOLATION || errorCode == ERROR_LOCK_VIOLATION))
            {
                return true;
            }
        }
        finally
        {
            if (stream != null)
                stream.Close();
        }
    }
    return false;
}