Get the list of files with multiple extensions filter

Question

Hello,
Using this:

Dim MySourceFiles As IEnumerable(Of String) = Nothing

MySourceFiles = Directory.EnumerateFiles(inDir, "*.ext1", SearchOption.TopDirectoryOnly)

But I need few more extensions to list and to be added to MySourceFiles, so another:

MySourceFiles += Directory.EnumerateFiles(inDir, "*.ext2", SearchOption.TopDirectoryOnly)

Just can't use +=
So how to list multiple file extensions and add them all to the MySourceFiles?
Thanks in advance :)

Answer 1

You may use the Union. Refer the following sample.

var result = Directory.EnumerateFiles("D:\\Temp\\Files", "*.jpg")  
    .Union(Directory.EnumerateFiles("D:\\Temp\\Files", "*.png"))  
    .Union(Directory.EnumerateFiles("D:\\Temp\\Files", "*.mp4"))  
    .ToList();  

To understand more about Union Method, read the below article

https://learn.microsoft.com/en-us/dotnet/api/system.linq.enumerable.union?view=net-7.0

Hope this helps

Answer 2

Hi
Late to the party, but here is my example (gleaned/modified from old google search sample), If time is critical then this example may help.

I incorporated @Sreeju Nair example to test differences. (all commented out)
The results seem to show this example to take about 60% of the time from first example. (for large data sets is significant)

Here is code for bot (need to rearrange stopwatch calls to try both. I just used my Visual studio Projects folder for testing purposes. File types can be added to 'filter' list as needed. I put results into a List(Of String) but could be anything.

    Dim sw As New Stopwatch  
    Dim path As String = "C:\Users\lesha\Documents\Projects"  
    Dim filter As String = "*.vb,*.resx"  
    Dim res As New List(Of String)  
    Dim counter As Integer = 0  
  
    'Do  
    '  Dim result As List(Of String) = Directory.EnumerateFiles(path, "*.vb", SearchOption.AllDirectories).Union(Directory.EnumerateFiles(path, "*.resx", SearchOption.AllDirectories)).ToList()  
    '  res.AddRange(result)  
    '  ' approx 625ms per cycle  
    '  counter += 1  
    'Loop Until counter = 20  
    'Dim t As Long = sw.ElapsedMilliseconds  
    'eg 12480ms for the 20 cycles  
  
    ' agreagated: average about 625ms per cycle on my system with 57560 results from 274000 total files  
  
    ' about 12693ms for all cycles  
    'counter = 0  
    'sw.Restart()  
    sw.Start()  
    Do  
      res.AddRange(filter.Split(","c).AsParallel().SelectMany(Function(x) Directory.EnumerateFiles(path, x, SearchOption.AllDirectories)).OrderBy(Function(x) x).ToArray())  
      'ex. 377ms per cycle  
  
      counter += 1  
    Loop Until counter = 20  
    Dim t As Long = sw.ElapsedMilliseconds  
    'ex. 7530ms for the 20 cycles  
  
    ' agreagated: average about 377ms per cycle on my system with 57560 results from 274000 total files  
    Stop  

Answer 3

Depending on the number of files in the folder v how many filtered you MIGHT be better off reading all of the names into a list and filtering that.