Using c# GetFiles Length but only count the files with certain amount of chars in filename

Question

So i'm using the simple

ImgFilesCount = ImgDirInfo.GetFiles("*.jpg").Length;

to figure out how many files are in a dir. But I need it to only count files that have exactly 26 characters in the file name. I tried

ImgFilesCount = ImgDirInfo.GetFiles("?????????????????????????.jpg").Length;

But it didn't work. Is the only option to do a foreach loop and check each filename and increment the counter? I have a feeling linq can probably do this with a .Where statement but I don't know any Linq.

.Where(fname => condition(fname.Length)) – Lennart May 17 '13 at 23:54 — Lennart, May 17 '13 at 23:54

score 5 · Accepted Answer · answered May 17 '13 at 23:55

5

Maybe

int count = ImgDirInfo.EnumerateFiles("*.jpg").Count(f => f.Name.Length == 26);

EnumerateFiles is more efficient since it doesn't need to load all files into memory before it starts processing.

When you use EnumerateFiles, you can start enumerating the collection of FileInfo objects before the whole collection is returned.
When you use GetFiles, you must wait for the whole array of FileInfo objects to be returned before you can access the array.

answered May 17 '13 at 23:55

Tim Schmelter

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Good point about `EnumerateFiles`. Just tiny note: isn't `Count` will load all files making streaming nature of `EnumerateFiles` irrelevant? – Ilya Ivanov May 17 '13 at 23:59
@IlyaIvanov Well, no. That's the whole beauty of iterators. The `Count` extension method consumes the query during the counting process. – SimpleVar May 18 '13 at 00:00
@YoryeNathan as result making more calls to hard disk? – Ilya Ivanov May 18 '13 at 00:02
@YoryeNathan: In this case Ilya is right since `Count` needs to enumerate all files with the given search pattern. So in general it's better to use `Directory.EnumerateFiles` instead if you only need the filename. – Tim Schmelter May 18 '13 at 00:03
@IlyaIvanov It's Performance vs Memory. I usually go for performance, but it depends on the situation. This is only to point out that in some cases the `EnumerateFiles` method is more appropriate *even though* it does consume the query in the end. – SimpleVar May 18 '13 at 00:03
@YoryeNathan agree, but it's hard to say where performance is better without empirical evidence. Anyway, I should definitely need to remember `EnumerateFiles`. I've knew about `ReadLines` vs `ReadAllLines`, now Tim brought another streaming vs non-streaming files reading, – Ilya Ivanov May 18 '13 at 00:05

score 3 · Answer 2 · answered May 17 '13 at 23:56

3

ImgFilesCount = ImgDirInfo.GetFiles("*.jpg")
                          .Where(file => file.Name.Length == 26)
                          .Count();

answered May 17 '13 at 23:56

Ilya Ivanov

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score 0 · Answer 3 · answered May 18 '13 at 00:05

0

Something like this?

        string[] files = Directory
                         .EnumerateFiles(@"c:\Users\x074\Downloads" , "*.jpg" , SearchOption.AllDirectories )
                         .Where( path => Path.GetFileName(path).Length > 20 )
                         .ToArray()
                         ;

answered May 18 '13 at 00:05

Nicholas Carey

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_"exactly 26 characters"_ is somewhat different to `Length > 20`. – Tim Schmelter May 18 '13 at 00:06

Using c# GetFiles Length but only count the files with certain amount of chars in filename

3 Answers3