Quickest way in C# to find a file in a directory with over 20,000 files

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Rather than doing GetFiles and doing a brute force search you could most likely use GetDirectories, first to get a list of the “First sub folder”, loop through those directories, then repeat the process for the sub folder, looping through them, lastly look for the xml folder, and finally searching for .xml files.

Now, as for performance the speed of this will vary, but searching for directories first, THEN getting to files should help a lot!

Update

Ok, I did a quick bit of testing and you can actually optimize it much further than I thought.

The following code snippet will search a directory structure and find ALL “xml” folders inside the entire directory tree.

string startPath = @"C:\Testing\Testing\bin\Debug";
string[] oDirectories = Directory.GetDirectories(startPath, "xml", SearchOption.AllDirectories);
Console.WriteLine(oDirectories.Length.ToString());
foreach (string oCurrent in oDirectories)
    Console.WriteLine(oCurrent);
Console.ReadLine();

If you drop that into a test console app you will see it output the results.

Now, once you have this, just look in each of the found directories for you .xml files.

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