How to make your VB .NET application scan sub-folders for files?

You must have heard about recursive programming. If not, then take a look of it on Wikipedia. In recursive programming, the function or method calls itself. This may seem confusing but after looking at the code below, it will be easy enough for you.

Code below scans entire file system and lists scanned files into a listbox named ‘scannedFiles’

Code Snippet

1. Public Class Form1
2.  
3.     Sub scanSubfolders(ByVal FolderLocation As String, ByVal List As ListBox)
4.         For Each s In My.Computer.FileSystem.GetFiles(FolderLocation)
5.             Try
6.                 List.Items.Add(s)
7.             Catch ex As Exception
8.  
9.             End Try
10.         Next
11.         For Each s In My.Computer.FileSystem.GetDirectories(FolderLocation)
12.             Try
13.                 scanSubfolders(s, List)
14.             Catch ex As Exception
15.  
16.             End Try
17.         Next
18.     End Sub
19.  
20.     Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
21.         BackgroundWorker1.RunWorkerAsync()
22.     End Sub
23.  
24.     Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
25.         CheckForIllegalCrossThreadCalls = False
26.         scanSubfolders("C:\", Me.scannedFiles)
27.     End Sub
28. End Class

In the above code, the sub scanSunfolders() is calling itself again in line 13.

The scanSubfolders() is the main part. Within lines 5 and 7, you can do almost everything. Since ‘s’ is the file for instant, you can add an ‘if’ statement between lines 5 and 7 that filters only those files whose filenames end with ‘.mp3’ or any other extension. I have added ‘Try…Catch…End Try’ statement to evade file access errors if scanning a protected folder. This has been further illustrated below:

Code Snippet

1. Sub scanSubfolders(ByVal FolderLocation As String, ByVal List As ListBox)
2.     For Each s In My.Computer.FileSystem.GetFiles(FolderLocation)
3.         Try
4.             If s.EndsWith(".mp3") Or s.EndsWith(".wav") Then
5.                 List.Items.Add(s)
6.             End If
7.         Catch ex As Exception
8.  
9.         End Try
10.     Next
11.     For Each s In My.Computer.FileSystem.GetDirectories(FolderLocation)
12.         Try
13.             scanSubfolders(s, List)
14.         Catch ex As Exception
15.  
16.         End Try
17.     Next
18. End Sub

Experiment with this code yourself. If you have any suggestions, problems or queries, please feel free to comment.