Скачать или смотреть Understanding the Default Sort Order of System.IO.Directory.GetFiles() and How to Customize It

Discover how `System.IO.Directory.GetFiles()` sorts filenames by default and learn how to customize the sorting by file creation date for more efficient file handling.
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This video is based on the question https://stackoverflow.com/q/52842/ asked by the user 'Joel Coehoorn' ( https://stackoverflow.com/u/3043/ ) and on the answer https://stackoverflow.com/a/52867/ provided by the user 'Ian Nelson' ( https://stackoverflow.com/u/2084/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Default Sorting of Directory.GetFiles() in .NET

When working with file systems in .NET, you might encounter the System.IO.Directory.GetFiles() method. This method retrieves files in a directory, returning them as a string array. However, a common question arises regarding how these files are sorted by default and whether you can customize this sorting. Let's dive deep into this topic, clarify the default behavior, and explore how to sort files based on different criteria, like creation date.

The Default Sort Order: What Happens When You Call GetFiles()?

When you use Directory.GetFiles(), it returns a string[], which contains the names of the files found in the specified directory. But what dictates the order of these filenames?

Sorting Behavior

Default Order: The default sort order for the results returned by GetFiles() is essentially not guaranteed. While it’s often assumed that files are sorted by name, there’s no explicit assurance about this behavior across different .NET versions, particularly in .NET 3.5 and beyond.

Cultural Influence: The sorting can also be affected by the current culture of the system running the code. Different cultures can influence how string comparison is executed, potentially resulting in varying orders for filenames.

Downtime with .NET 2.0: No Guarantees, No Metadata

If you’re working with .NET 2.0, you might be puzzled by the lack of documentation regarding the sort order of GetFiles(). It’s crucial to understand that once you retrieve the filenames, any metadata related to creation or modification dates is lost. You receive only strings without a direct link to their properties.

How to Customize File Sorting by Properties

If you’re interested in sorting by criteria such as file creation time or modification time, using DirectoryInfo.GetFileSystemInfos() is a more effective approach.

Step-by-Step Guide to Access and Sort Files by Creation Date

Use DirectoryInfo Instead of GetFiles: Begin by creating an instance of DirectoryInfo for the desired directory.

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Retrieve FileSystemInfo Objects: Call GetFileSystemInfos() to get an array of FileSystemInfo, which holds more than just the filename.

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Sort Files: You can sort these files based on their CreationTime or any other property you are interested in. Using LINQ (this is relevant for .NET 3.5 and beyond) makes this easy:

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Note: Ensure that you have using System.Linq; at the top of your file to access the LINQ extension methods.

Conclusion: The Right Tool for Accurate File Handling

To summarize, while Directory.GetFiles() operates under an uncertain sort order, using DirectoryInfo.GetFileSystemInfos() provides the opportunity to work with files in a more meaningful way, including customizing the order based on file properties. This approach not only offers greater flexibility but also keeps your code efficient by avoiding unnecessary file system accesses after initial retrieval.

In your next file handling project, remember to leverage these methods to ensure you can sort and manage your files more effectively!