You will need to use the IO.Directory.GetFiles function.

Dim files() As String = IO.Directory.GetFiles("c:")

For Each file As String In files
  ' Do work, example
  Dim text As String = IO.File.ReadAllText(file)
Next

Dim fileEntries As String() = Directory.GetFiles("YourPath", "*.txt")
' Process the list of .txt files found in the directory. '
Dim fileName As String

For Each fileName In fileEntries
    If (System.IO.File.Exists(fileName)) Then
        'Read File and Print Result if its true
        ReadFile(fileName)
    End If
    TransfereFile(fileName, 1)
Next

System.IO.Directory.GetFiles() 

could help

Try this:

Dim text As String = ""
Dim files() As String = IO.Directory.GetFiles(sFolder)

For Each sFile As String In files
    text &= IO.File.ReadAllText(sFile)
Next

Public PathsAll As String 'is All Path Finded
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Dim BeginPath As String = "D:" 'this is Begin Path
    FilesSearch(BeginPath)
    'TextBox1.Text = AddPath
End Sub
Public Sub FilesSearch(BeginPath As String)
    Dim arrFolders(0) As String
    Dim TmpDir As String
    Dim arrFiles As String
    Dim countDir As Integer = 0
    arrFolders(countDir) = ""
    If Microsoft.VisualBasic.Right(BeginPath, 1) <> "" Then
        BeginPath = BeginPath & ""
    End If
    TmpDir = Dir(BeginPath, vbDirectory)
    ' On Error Resume Next
    Do While TmpDir <> ""
        AppendFiles(BeginPath & TmpDir)
        If TmpDir <> "." And TmpDir <> ".." Then
            If (GetAttr(BeginPath & TmpDir) And vbDirectory) = vbDirectory Then
                arrFolders(countDir) = BeginPath & TmpDir & ""
                countDir += 1
                ReDim Preserve arrFolders(countDir)
            End If
        End If
        TmpDir = Dir()
    Loop
    arrFiles = Dir(BeginPath)
    Do Until arrFiles = ""
        arrFiles = Dir()
    Loop
    For X = 0 To (UBound(arrFolders) - 1)
        FilesSearch(arrFolders(X))
    Next X
End Sub
Public Sub AppendFiles(InPath As String)
    PathsAll += vbNewLine & InPath
End Sub