C# 如何使用 .NET 在目录中查找最新的文件，并且不循环？

How to find the most recent file in a directory using .NET, and without looping?

提问by Chris Klepeis

I need to find the most recently modified file in a directory.

我需要在目录中找到最近修改的文件。

I know I can loop through every file in a folder and compare File.GetLastWriteTime, but is there a better way to do this without looping?.

我知道我可以遍历文件夹中的每个文件并比较File.GetLastWriteTime，但是有没有更好的方法来做到这一点而不循环？

采纳答案by Scott Ivey

how about something like this...

这样的事情怎么样...

var directory = new DirectoryInfo("C:\MyDirectory");
var myFile = (from f in directory.GetFiles()
             orderby f.LastWriteTime descending
             select f).First();

// or...
var myFile = directory.GetFiles()
             .OrderByDescending(f => f.LastWriteTime)
             .First();

回答by Scott Marlowe

You can react to new file activity with FileSystemWatcher.

您可以使用FileSystemWatcher对新文件活动做出反应。

回答by TimothyP

A non-LINQ version:

非 LINQ 版本：

/// <summary>
/// Returns latest writen file from the specified directory.
/// If the directory does not exist or doesn't contain any file, DateTime.MinValue is returned.
/// </summary>
/// <param name="directoryInfo">Path of the directory that needs to be scanned</param>
/// <returns></returns>
private static DateTime GetLatestWriteTimeFromFileInDirectory(DirectoryInfo directoryInfo)
{
    if (directoryInfo == null || !directoryInfo.Exists)
        return DateTime.MinValue;

    FileInfo[] files = directoryInfo.GetFiles();
    DateTime lastWrite = DateTime.MinValue;

    foreach (FileInfo file in files)
    {
        if (file.LastWriteTime > lastWrite)
        {
            lastWrite = file.LastWriteTime;
        }
    }

    return lastWrite;
}

/// <summary>
/// Returns file's latest writen timestamp from the specified directory.
/// If the directory does not exist or doesn't contain any file, null is returned.
/// </summary>
/// <param name="directoryInfo">Path of the directory that needs to be scanned</param>
/// <returns></returns>
private static FileInfo GetLatestWritenFileFileInDirectory(DirectoryInfo directoryInfo)
{
    if (directoryInfo == null || !directoryInfo.Exists)
        return null;

    FileInfo[] files = directoryInfo.GetFiles();
    DateTime lastWrite = DateTime.MinValue;
    FileInfo lastWritenFile = null;

    foreach (FileInfo file in files)
    {
        if (file.LastWriteTime > lastWrite)
        {
            lastWrite = file.LastWriteTime;
            lastWritenFile = file;
        }
    }
    return lastWritenFile;
}

回答by Edgar Villegas Alvarado

If you want to search recursively, you can use this beautiful piece of code:

如果你想递归搜索，你可以使用这段漂亮的代码：

public static FileInfo GetNewestFile(DirectoryInfo directory) {
   return directory.GetFiles()
       .Union(directory.GetDirectories().Select(d => GetNewestFile(d)))
       .OrderByDescending(f => (f == null ? DateTime.MinValue : f.LastWriteTime))
       .FirstOrDefault();                        
}

Just call it the following way:

只需按以下方式调用它：

FileInfo newestFile = GetNewestFile(new DirectoryInfo(@"C:\directory\"));

and that's it. Returns a FileInfoinstance or nullif the directory is empty.

就是这样。返回一个FileInfo实例或null目录是否为空。

回答by Sylver1981

private List<FileInfo> GetLastUpdatedFileInDirectory(DirectoryInfo directoryInfo)
{
    FileInfo[] files = directoryInfo.GetFiles();
    List<FileInfo> lastUpdatedFile = null;
    DateTime lastUpdate = new DateTime(1, 0, 0);
    foreach (FileInfo file in files)
    {
        if (file.LastAccessTime > lastUpdate)
        {
            lastUpdatedFile.Add(file);
            lastUpdate = file.LastAccessTime;
        }
    }

    return lastUpdatedFile;
}

回答by Zamir

Expanding on the first one above, if you want to search for a certain pattern you may use the following code:

扩展上面的第一个，如果您想搜索某个模式，您可以使用以下代码：

string pattern = "*.txt";
var dirInfo = new DirectoryInfo(directory);
var file = (from f in dirInfo.GetFiles(pattern) orderby f.LastWriteTime descending select f).First();

回答by Michael Bahig

Here's a version that gets the most recent file from each subdirectory

这是一个从每个子目录中获取最新文件的版本

List<string> reports = new List<string>();    
DirectoryInfo directory = new DirectoryInfo(ReportsRoot);
directory.GetFiles("*.xlsx", SearchOption.AllDirectories).GroupBy(fl => fl.DirectoryName)
.ForEach(g => reports.Add(g.OrderByDescending(fi => fi.LastWriteTime).First().FullName));

回答by Oleg Karbushev

it's a bit late but...

有点晚了但是...

your code will not work, because of list<FileInfo> lastUpdateFile = null;and later lastUpdatedFile.Add(file);so NullReference exception will be thrown. Working version should be:

您的代码将无法工作，因为list<FileInfo> lastUpdateFile = null;稍后lastUpdatedFile.Add(file);将抛出 NullReference 异常。工作版本应该是：

private List<FileInfo> GetLastUpdatedFileInDirectory(DirectoryInfo directoryInfo)
{
    FileInfo[] files = directoryInfo.GetFiles();
    List<FileInfo> lastUpdatedFile = new List<FileInfo>();
    DateTime lastUpdate = DateTime.MinValue;
    foreach (FileInfo file in files)
    {
        if (file.LastAccessTime > lastUpdate)
        {
            lastUpdatedFile.Add(file);
            lastUpdate = file.LastAccessTime;
        }
    }

    return lastUpdatedFile;
}

Thanks

谢谢

回答by JasonR

I do this is a bunch of my apps and I use a statement like this:

我这样做是我的一堆应用程序，我使用这样的语句：

  var inputDirectory = new DirectoryInfo("\Directory_Path_here");
  var myFile = inputDirectory.GetFiles().OrderByDescending(f => f.LastWriteTime).First();

From here you will have the filename for the most recently saved/added/updated file in the Directory of the "inputDirectory" variable. Now you can access it and do what you want with it.

从这里，您将在“inputDirectory”变量的目录中获得最近保存/添加/更新的文件的文件名。现在您可以访问它并使用它做您想做的事情。

Hope that helps.

希望有帮助。

回答by Jacob

Short and simple:

简短而简单：

new DirectoryInfo(path).GetFiles().OrderByDescending(o => o.LastWriteTime).FirstOrDefault();