.NET FileInfo.LastWriteTime & FileInfo.LastAccessTime are wrong

Answer 1

Have you tried calling Refresh() just before accessing the property (to avoid getting a cached value)? If that doesn't work, have you looked at what Explorer shows at the same time? If Explorer is showing the wrong information, then it's probably something you can't really address - it might be that the information is only updated when the file handle is closed, for example.

Answer 2

The FileInfo values are only loaded once and then cached. To get the current value, call Refresh() before getting a property:

f.Refresh();
t = f.LastAccessTime;

Another way to get the current value is by using the static methods on the File-class:

t = File.GetLastAccessTime(path);

Answer 3

From MSDN:

When first called, FileSystemInfo calls Refresh and returns the cached information on APIs to get attributes and so on. On subsequent calls, you must call Refresh to get the latest copy of the information.

FileSystemInfo.Refresh()

If you're application is the one doing the writing, I think you are going to have to "touch" the file by setting the LastWriteTime property your self between each buffer of data you write. Some psuedocode:

while(bytesWritten < totalBytes)
{
   bytesWritten += br.Write(buffer);
   myFileInfo.LastWriteTime = DateTime.Now;
}

I'm not sure how severely this will affect write performance.

Answer 4

There is a setting in windows which is sometimes set especially on server systems so that modified and accessed times for files are not set for better performance.