Can you call Directory.GetFiles() with multiple filters?

Another way to use Linq, but without having to return everything and filter on that in memory.

var files = Directory.GetFiles("C:\\path", "*.mp3", SearchOption.AllDirectories).Union(Directory.GetFiles("C:\\path", "*.jpg", SearchOption.AllDirectories));

It's actually 2 calls to GetFiles(), but I think it's consistent with the spirit of the question and returns them in one enumerable.

DirectoryInfo directory = new DirectoryInfo(Server.MapPath("~/Contents/"));

//Using Union

FileInfo[] files = directory.GetFiles("*.xlsx")
                            .Union(directory
                            .GetFiles("*.csv"))
                            .ToArray();

I wonder why there are so many "solutions" posted?

If my rookie-understanding on how GetFiles works is right, there are only two options and any of the solutions above can be brought down to these:

1. GetFiles, then filter: Fast, but a memory killer due to storing overhead untill the filters are applied

2. Filter while GetFiles: Slower the more filters are set, but low memory usage as no overhead is stored.
   This is explained in one of the above posts with an impressive benchmark: Each filter option causes a seperate GetFile-operation so the same part of the harddrive gets read several times.

In my opinion Option 1) is better, but using the SearchOption.AllDirectories on folders like C:\ would use huge amounts of memory.
Therefor i would just make a recursive sub-method that goes through all subfolders using option 1)

This should cause only 1 GetFiles-operation on each folder and therefor be fast (Option 1), but use only a small amount of memory as the filters are applied afters each subfolders' reading -> overhead is deleted after each subfolder.

Please correct me if I am wrong. I am as i said quite new to programming but want to gain deeper understanding of things to eventually become good at this :)