Multiple file-extensions searchPattern for System.IO.Directory.GetFiles

Question

What is the syntax for setting multiple file-extensions as searchPattern on Directory.GetFiles()? For example filtering out files

Answer 1

A more efficient way of getting files with the extensions ".aspx" and ".ascx" that avoids querying the file system several times and avoids returning a lot of undesired files, is to pre-filter the files by using an approximate search pattern and to refine the result afterwards:

var filteredFiles = Directory.GetFiles(path, "*.as?x")
    .Select(f => f.ToLowerInvariant())
    .Where(f => f.EndsWith("px") || f.EndsWith("cx"))
    .ToList();