How do you know if a file is still be written to?

[napstar]

I'm copying files generated by an application periodically to my PC from a network location,but sometimes the files are still be written when I copy them.
How can I tell if the file is still be written to?

public void copyFile(string source, string destination)
{
DirectoryInfo dir = new DirectoryInfo(source);
FileInfo[] files = dir.GetFiles();
foreach (FileInfo f in files)
{
DateTime currentTime = DateTime.Now;

DateTime tolerance = currentTime.Subtract(new TimeSpan(0, 5, 0));
if (tolerance.CompareTo(f.LastWriteTime) > 0)
{


f.CopyTo(destination + "" + f.Name, true);


}
}//end of foreach
}

[Plater]

I posted a potential solution to this in another thread but I don't think the OP ever got back if it worked or not. I think it will.

Try to open the file with READ+WRITE access and be exclusive, say no sharring allowed. I *think* it will throw an exception if the file is still being "written" to when you try that, so that is one way to tell.