Monitoring files - how to know when a file is complete

Question

We have several .NET applications that monitor a directory for new files, using FileSystemWatcher. The files are copied from another location, uploaded via FTP, etc. When th

Answer 1

The following method tries to open a file with write permissions. It will block execution until a file is completely written to disk:

/// 

/// Waits until a file can be opened with write permission
/// 
public static void WaitReady(string fileName)
{
    while (true)
    {
        try
        {
            using (System.IO.Stream stream = System.IO.File.Open(fileName, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite))
            {
                if (stream != null)
                {
                    System.Diagnostics.Trace.WriteLine(string.Format("Output file {0} ready.", fileName));
                    break;
                }
            }
        }
        catch (FileNotFoundException ex)
        {
            System.Diagnostics.Trace.WriteLine(string.Format("Output file {0} not yet ready ({1})", fileName, ex.Message));
        }
        catch (IOException ex)
        {
            System.Diagnostics.Trace.WriteLine(string.Format("Output file {0} not yet ready ({1})", fileName, ex.Message));
        }
        catch (UnauthorizedAccessException ex)
        {
            System.Diagnostics.Trace.WriteLine(string.Format("Output file {0} not yet ready ({1})", fileName, ex.Message));
        }
        Thread.Sleep(500);
    }
}

(from my answer to a related question)