如何过滤具有特定扩展名的 Directory.EnumerateFiles

Question

I want a list of all xml files in a folder like this:

foreach (var file in Directory.EnumerateFiles(folderPath, "*.xml"))
{
    // add file to a collection
}

However, if I for some reason have any files in folderPath that ends with .xmlXXX where XXX represent any characters, then they will be part of the enumerator.

If can solve it easily by doing something like

foreach (var file in Directory.EnumerateFiles(folderPath, "*.xml").Where(x => x.EndsWith(".xml")))

But it seems a bit odd to me, as I basically have to search for the same thing two times. Is there any way to get the right files directly or am I doing something wrong?

Answer 1

The is the documented/default behaviour of the wildcard usage with file searching.

Directory.EnumerateFiles Method (String, String)

If the specified extension is exactly three characters long, the method returns files with extensions that begin with the specified extension. For example, "*.xls" returns both "book.xls" and "book.xlsx".

Your current approach of filtering twice is the right way.

The only improvement you can do is to ignore case in EndsWith like:

x.EndsWith(".xml", StringComparison.CurrentCultureIgnoreCase)

Answer 2

It seems like you cant do it using EnumerateFiles for 3 characters extension, according to MSDN

Quote from the article above

When you use the asterisk wildcard character in a searchPattern such as " .txt", the number of characters in the specified extension affects the search as follows: If the specified extension is exactly three characters long, the method returns files with extensions that begin with the specified extension. For example, " .xls" returns both "book.xls" and "book.xlsx". In all other cases, the method returns files that exactly match the specified extension. For example, " .ai" returns "file.ai" but not "file.aif". When you use the question mark wildcard character, this method returns only files that match the specified file extension. For example, given two files, "file1.txt" and "file1.txtother", in a directory, a search pattern of "file?.txt" returns just the first file, whereas a search pattern of "file .txt" returns both files.

Therefore using the .Where extension seems like the best solution to your problem

Answer 3

Yes, and this design is stupid, stupid, stupid! It shouldn't do that. And it's annoying too!

That said, it appears this is what is happening: It actually searches both the long and short filenames. So files with longer extensions will have a short filename with the extension truncated to three characters.

And on newer versions of Windows, the short filenames may be disabled. So the behavior on newer systems will actually be what you would expect, and what it should've been in the first place.