Configuration SearchPattern in EnumerateFiles

Question

I have a directory with 2 files:

• file1.xls
• file2.xlsx

If I do:

directoryInfo.EnumerateFiles("*.xls", SearchOption.TopDirectoryOnly)

It is returning both files, and I only want the first (file1.xls). How can I do this?

Thank you!

Answer 1

It looks like under the hood, the DirectoryInfo class uses the Win32 call FindFirstFile.

This only allows the wildcards:

* to match any character

? to match 0 or more characters - see comments.

Therefore you will have to filter the results yourself, perhaps using the following:

directoryInfo.EnumerateFiles("*.xls", SearchOption.TopDirectoryOnly)
             .Where(fi => fi.Extension == ".xls");

Answer 2

This is actually an expected behaviour. It's odd, but it is documented.

On MSDN we can read a remark:

When using the asterisk wildcard character in a searchPattern, such as "*.txt", the matching behavior when the extension is exactly three characters long is different than when the extension is more or less than three characters long. A searchPattern with a file extension of exactly three characters returns files having an extension of three or more characters, where the first three characters match the file extension specified in the searchPattern. A searchPattern with a file extension of one, two, or more than three characters returns only files having extensions of exactly that length that match the file extension specified in the searchPattern. When using 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, while a search pattern of "file*.txt" returns both files.