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

I like this method, because it is readable and avoids multiple iterations of the directory:

var allowedExtensions = new [] {".doc", ".docx", ".pdf", ".ppt", ".pptx", ".xls", ".xslx"}; 
var files = Directory
    .GetFiles(folder)
    .Where(file => allowedExtensions.Any(file.ToLower().EndsWith))
    .ToList();