FileSystemWatcher - 文件复制期间的3个事件

Question

Is that, every time FileSystemWatcher will generate 3 events when a file is copied to the FileWatcher folder

Example : Am getting Created - > Changed -> Changed (during new file) Or Changed - > Changed - > Changed (during overwrite of existing file) event , when file is copied to the FileWatcher folder using File.Copy(source,watcherFolder,true).

Am getting 3 events when copying file of different size (1kb , 67kb, 100MB, 500MB, 1 GB files). i have registerd for Created and Changed event in FileSystemWatcher

Answer 1

If your question is about the multiple events you are receiving, this is a normal behavior. File copy can raise multiple event.

You can check the changes in FileSystemEventArgs.ChangeType and ignore some of the events. Here is the WatcherChangeTypes Enumeration .

Take a look at FileSystemWatcher Remarks.

About the Created event, it will be raised in the destination folder.

For example, you create two instances of FileSystemWatcher. FileSystemWatcher1 is set to watch "C:\\My Documents", and FileSystemWatcher2 is set to watch "C:\\Your Documents". If you copy a file from "My Documents" into "Your Documents", a Created event will be raised by FileSystemWatcher2, but no event is raised for FileSystemWatcher1. Unlike copying, moving a file or directory would raise two events. From the previous example, if you moved a file from "My Documents" to "Your Documents", a Created event would be raised by FileSystemWatcher2 and a Deleted event would be raised by FileSystemWatcher1.

Answer 2

As mentioned in the comments, you should look for a file being created and then attempt a file lock to determine if it is fully copied.

    while ($true)
    {
        try{ 
            [IO.file]::openwrite("<insert file path>").close()
            break
        }
        catch { start-sleep -Seconds 60 }
    }

Answer 3

If you are in control of the file copy operation, a simple thing to do is to create the file with a temporary name and rename it once it has been copied. Let the FileSystemWatcher watch for the Rename event. This event is fired only once.