Testing if a file is complete

Question

I am kinda new to C#, so please bear with me.
What is the easiest way to test if a file is complete?
Let me explain. A company outside is sending us text files throughout the day. They can range is size from several thousand bytes to almost  250 megs. My program runs from a Scheduled Task throughout the day. The short files are usually no problem, but the big ones can be and often are still in the process of being transmitted into the directory from outside.
The way I have been testing this is to try and rename the file. If I get an exception, I know its still writing. Is there an easier way to test that a file is complete?
Thanks
Frank

Sam Hobbs · Answer

I think you should use the FileSystemWatcher class. I don't know if it rasies an event when a file is closed but I think you should use the FileSystemWatcher class at least. You can test to see if you get notification whe a file that has beeen created is closed.

Mahesh Chand · Answer

So I am assuming that you do not have a UI or console to display the progress? What I would do is, display progress in the UI. If this work is being done in a service, you can write to a log file the progress. OR display a message when the file reading is done.