Loop through files in a folder using VBA?

Dir takes wild cards so you could make a big difference adding the filter for test up front and avoiding testing each file

Sub LoopThroughFiles()
    Dim StrFile As String
    StrFile = Dir("c:\testfolder\*test*")
    Do While Len(StrFile) > 0
        Debug.Print StrFile
        StrFile = Dir
    Loop
End Sub

Here's my interpretation as a Function Instead:

'#######################################################################
'# LoopThroughFiles
'# Function to Loop through files in current directory and return filenames
'# Usage: LoopThroughFiles ActiveWorkbook.Path, "txt" 'inputDirectoryToScanForFile
'# https://stackoverflow.com/questions/10380312/loop-through-files-in-a-folder-using-vba
'#######################################################################
Function LoopThroughFiles(inputDirectoryToScanForFile, filenameCriteria) As String

    Dim StrFile As String
    'Debug.Print "in LoopThroughFiles. inputDirectoryToScanForFile: ", inputDirectoryToScanForFile

    StrFile = Dir(inputDirectoryToScanForFile & "\*" & filenameCriteria)
    Do While Len(StrFile) > 0
        Debug.Print StrFile
        StrFile = Dir

    Loop

End Function

The Dir function is the way to go, but the problem is that you cannot use the Dir function recursively, as stated here, towards the bottom.

The way that I've handled this is to use the Dir function to get all of the sub-folders for the target folder and load them into an array, then pass the array into a function that recurses.

Here's a class that I wrote that accomplishes this, it includes the ability to search for filters. (You'll have to forgive the Hungarian Notation, this was written when it was all the rage.)

Private m_asFilters() As String
Private m_asFiles As Variant
Private m_lNext As Long
Private m_lMax As Long

Public Function GetFileList(ByVal ParentDir As String, Optional ByVal sSearch As String, Optional ByVal Deep As Boolean = True) As Variant
    m_lNext = 0
    m_lMax = 0

    ReDim m_asFiles(0)
    If Len(sSearch) Then
        m_asFilters() = Split(sSearch, "|")
    Else
        ReDim m_asFilters(0)
    End If

    If Deep Then
        Call RecursiveAddFiles(ParentDir)
    Else
        Call AddFiles(ParentDir)
    End If

    If m_lNext Then
        ReDim Preserve m_asFiles(m_lNext - 1)
        GetFileList = m_asFiles
    End If

End Function

Private Sub RecursiveAddFiles(ByVal ParentDir As String)
    Dim asDirs() As String
    Dim l As Long
    On Error GoTo ErrRecursiveAddFiles
    'Add the files in 'this' directory!


    Call AddFiles(ParentDir)

    ReDim asDirs(-1 To -1)
    asDirs = GetDirList(ParentDir)
    For l = 0 To UBound(asDirs)
        Call RecursiveAddFiles(asDirs(l))
    Next l
    On Error GoTo 0
Exit Sub
ErrRecursiveAddFiles:
End Sub
Private Function GetDirList(ByVal ParentDir As String) As String()
    Dim sDir As String
    Dim asRet() As String
    Dim l As Long
    Dim lMax As Long

    If Right(ParentDir, 1) <> "\" Then
        ParentDir = ParentDir & "\"
    End If
    sDir = Dir(ParentDir, vbDirectory Or vbHidden Or vbSystem)
    Do While Len(sDir)
        If GetAttr(ParentDir & sDir) And vbDirectory Then
            If Not (sDir = "." Or sDir = "..") Then
                If l >= lMax Then
                    lMax = lMax + 10
                    ReDim Preserve asRet(lMax)
                End If
                asRet(l) = ParentDir & sDir
                l = l + 1
            End If
        End If
        sDir = Dir
    Loop
    If l Then
        ReDim Preserve asRet(l - 1)
        GetDirList = asRet()
    End If
End Function
Private Sub AddFiles(ByVal ParentDir As String)
    Dim sFile As String
    Dim l As Long

    If Right(ParentDir, 1) <> "\" Then
        ParentDir = ParentDir & "\"
    End If

    For l = 0 To UBound(m_asFilters)
        sFile = Dir(ParentDir & "\" & m_asFilters(l), vbArchive Or vbHidden Or vbNormal Or vbReadOnly Or vbSystem)
        Do While Len(sFile)
            If Not (sFile = "." Or sFile = "..") Then
                If m_lNext >= m_lMax Then
                    m_lMax = m_lMax + 100
                    ReDim Preserve m_asFiles(m_lMax)
                End If
                m_asFiles(m_lNext) = ParentDir & sFile
                m_lNext = m_lNext + 1
            End If
            sFile = Dir
        Loop
    Next l
End Sub

Dir seems to be very fast.

Sub LoopThroughFiles()
    Dim MyObj As Object, MySource As Object, file As Variant
   file = Dir("c:\testfolder\")
   While (file <> "")
      If InStr(file, "test") > 0 Then
         MsgBox "found " & file
         Exit Sub
      End If
     file = Dir
  Wend
End Sub