如何获取最新（最后修改）的目录[C＃]

Question

Currently my application uses string[] subdirs = Directory.GetDirectories(path) to get the list of subdirectories, and now I want to extract the path to the latest (last modified) subdirectory in the list.

What is the easiest way to accomplish this? (efficiency is not a major concern - but robustness is)

Answer 1

Non-recursive:

new DirectoryInfo(path).GetDirectories()
                       .OrderByDescending(d=>d.LastWriteTimeUtc).First();

Recursive:

new DirectoryInfo(path).GetDirectories("*", 
    SearchOption.AllDirectories).OrderByDescending(d=>d.LastWriteTimeUtc).First();

Answer 2

without using LINQ

DateTime lastHigh = new DateTime(1900,1,1);
string highDir;
foreach (string subdir in Directory.GetDirectories(path)){
    DirectoryInfo fi1 = new DirectoryInfo(subdir);
    DateTime created = fi1.LastWriteTime;

    if (created > lastHigh){
        highDir = subdir;
        lastHigh = created;
    }
}

Answer 3

Be warned: You might need to call Refresh() on your Directory Info object to get the correct information:

eg in Laramie's answer you'd edit to:

DirectoryInfo fi1 = new DirectoryInfo(subdir);
fi1.Refresh();
DateTime created = fi1.LastWriteTime;

Otherwise you might get outdated info like I did:

"Calls must be made to Refresh before attempting to get the attribute information, or the information will be outdated."

http://msdn.microsoft.com/en-us/library/system.io.filesysteminfo.refresh(v=vs.71).aspx

Answer 4

Try this:

string pattern = "*.txt"

var dirInfo = new DirectoryInfo(directory);

var file = (from f in dirInfo.GetFiles(pattern) 
            orderby f.LastWriteTime descending 
            select f).First();

http://zamirsblog.blogspot.com/2012/07/c-find-most-recent-file-in-directory.html

Answer 5

You can use Directory.GetLastWriteTime (or Directory.GetLastWriteTimeUtc , it doesn't really matter in this case when you're just doing relative comparisons).

Although do you just want to look at the "modified" time as reported by the OS, or do you want to find the directory with the most recently-modified file inside it? They don't always match up (that is, the OS doesn't always update the containing directory "last modified" time when it modifies a file).

Answer 6

If you are building a windows service and you want to be notified when a new file or directory is created you could also use a FileSystemWatcher . Admittedly not as easy, but interesting to play with. :)