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POList duplicate files inside a folder in C#: Leveraging LINQ.AsParallel
 

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  1. POList duplicate files inside a folder in C#: Leveraging LINQ.AsParallel
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    <p>I have written following algorithm into C# code to list down the files inside a folder recursively.</p> <ol> <li>Begin Iterating through the list of files in the directory &amp; its sub directories.</li> <li>Store file Name &amp; Path in a list.</li> <li>If current file matches any other file in the list, during mark both files as duplicate.</li> <li>Fetch all files from the list which were marked duplicate.</li> <li>Group them by name &amp; return.</li> </ol> <p>The implementation is very slow on a folder containing 50,000 files and 12,000 sub directories. As disk read operation is basically time consuming task. Even <strong>LINQ.Parallel()</strong> doesn't help much.</p> <p><strong>Implmentation:</strong></p> <blockquote> <pre><code>class FileTuple { public string FileName { set; get; } public string ContainingFolder { set; get; } public bool HasDuplicate { set; get; } public override bool Equals(object obj) { if (this.FileName == (obj as FileTuple).FileName) return true; return false; } } </code></pre> </blockquote> <ol> <li>FileTuple class keeps track of filenames &amp; containing directory, the flag keeps track of duplicate status.</li> <li>I have overridden the equals method to compare only files names, in the collection of fileTuples.</li> </ol> <p>Following method finds the duplicate files and return as a list.</p> <pre><code> private List&lt;FileTuple&gt; FindDuplicates() { List&lt;FileTuple&gt; fileTuples = new List&lt;FileTuple&gt;(); //Read all files from the given path List&lt;string&gt; enumeratedFiles = Directory.EnumerateFiles(txtFolderPath.Text, "*.*", SearchOption.AllDirectories).Where(str =&gt; str.Contains(".exe") || str.Contains(".zip")).AsParallel().ToList(); foreach (string filePath in enumeratedFiles) { var name = Path.GetFileName(filePath); var folder = Path.GetDirectoryName(filePath); var currentFile = new FileTuple { FileName = name, ContainingFolder = folder, HasDuplicate = false, }; int foundIndex = fileTuples.IndexOf(currentFile); //mark both files as duplicate, if found in list //assuming only two duplicate file if (foundIndex != -1) { currentFile.HasDuplicate = true; fileTuples[foundIndex].HasDuplicate = true; } //keep of track of the file navigated fileTuples.Add(currentFile); } List&lt;FileTuple&gt; duplicateFiles = fileTuples.Where(fileTuple =&gt; fileTuple.HasDuplicate).Select(fileTuple =&gt; fileTuple).OrderBy(fileTuple =&gt; fileTuple.FileName).AsParallel().ToList(); return duplicateFiles; } </code></pre> <p>Can you please suggest a way to improve the performance. </p> <p>Thank you for your help.</p>
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    1. COFor one, your code cannot produce any matches because `str.Contains("*.exe")` is false for all file names because of the star.
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    2. COSecond, you are in an imperative mindset. You are adding things to a list and such. State mutation is not good, neither in sequential nor in concurrent code. Instead, you should be grouping on the file name and looking for groups where `Count() > 1`.
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    3. COTypo, have rectified, thanks for pointing out.
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