один из вариантов реализации поиска файлов, средствами, которые предоставляет студия!

а оптимизация его это уже дело рук автора поста

Слушай тебе уже готовый рабочий пример показали(с одномерным массивом)? а ты все пыль подымаешь?

а давайте использовать FindFirstFile FindNextFile, перепишем пространство имен System.IO на ассемблере, например! я не говорил что мой код самый быстрый, это один из вариантов реализации поиска файлов, средствами, которые предоставляет студия!

Option Strict On

Imports System.IO

Public Class Form1

    im Directories As New Dictionary(Of String, List(Of String))
    im Files As New Dictionary(Of String, List(Of String))

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        im Start = Now
        PreLoad()
        MessageBox.Show(Now.Subtract(Start).ToString)
    End Sub

    Sub PreLoad()
        For Each Drive In DriveInfo.GetDrives
            If Drive.DriveType = DriveType.Fixed Then
                LoadDirectory(Drive.RootDirectory.FullName)
            End If
        Next
    End Sub

    Sub LoadDirectory(ByVal directory As String)
        Try
            im SubDirectories = IO.Directory.GetDirectories(directory)
            im SubFiles = IO.Directory.GetFiles(directory)

            im SubDirectoriesList = New List(Of String)(SubDirectories.Length)
            im SubFilesList = New List(Of String)(SubFiles.Length)
            irectories(directory.ToLower) = SubDirectoriesList
            Files(directory.ToLower) = SubFilesList

            For Each SubDirectory In SubDirectories
                SubDirectoriesList.Add(SubDirectory.ToLower)
                LoadDirectory(SubDirectory)
            Next
            For Each File In SubFiles
                SubFilesList.Add(File.ToLower)
            Next
        Catch ex As System.UnauthorizedAccessException
            ' все хорошо
        Catch ex As Exception
            Stop
        End Try
        
    End Sub

    Private Sub TextBox1_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
        im Directory As String = Nothing
        If Directories.ContainsKey(TextBox1.Text.ToLower) Then
            irectory = TextBox1.Text.ToLower
        ElseIf Directories.ContainsKey(TextBox1.Text.ToLower + "\" Then
            irectory = TextBox1.Text.ToLower + "\"
        ElseIf TextBox1.Text.Length > 0 AndAlso Directories.ContainsKey(TextBox1.Text.ToLower.Substring(0, TextBox1.Text.Length - 1)) Then
            irectory = TextBox1.Text.ToLower.Substring(0, TextBox1.Text.Length - 1)
        End If

        If Directory IsNot Nothing Then
            im ChildFiles As New List(Of String)
            FilesCount.Text = GetContent(Directory, ChildFiles).ToString
            irectoryFiles.DataSource = ChildFiles
        Else
            FilesCount.Text = ""
            irectoryFiles.DataSource = Nothing
        End If
    End Sub

    Function GetContent(ByVal directory As String, ByRef childFiles As List(Of String)) As Integer
        im Count = 0
        If Files.ContainsKey(directory) Then
            im F = Files(directory)
            Count = F.Count
            If childFiles.Count < 1000 Then
                childFiles.AddRange(F)
            End If
        End If

        If Directories.ContainsKey(directory) Then
            For Each SubDirectory In Directories(directory)
                Count += GetContent(SubDirectory, childFiles)
            Next
        End If
        Return Count
    End Function
End Class

<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
Partial Class Form1
    Inherits System.Windows.Forms.Form

    'Form overrides dispose to clean up the component list.
    <System.Diagnostics.DebuggerNonUserCode()> _
    Protected Overrides Sub Dispose(ByVal disposing As Boolean)
        Try
            If disposing AndAlso components IsNot Nothing Then
                components.Dispose()
            End If
        Finally
            MyBase.Dispose(disposing)
        End Try
    End Sub

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.IContainer

    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.  
    'Do not modify it using the code editor.
    <System.Diagnostics.DebuggerStepThrough()> _
    Private Sub InitializeComponent()
        Me.TextBox1 = New System.Windows.Forms.TextBox
        Me.Label1 = New System.Windows.Forms.Label
        Me.FilesCount = New System.Windows.Forms.Label
        Me.DirectoryFiles = New System.Windows.Forms.ListBox
        Me.SuspendLayout()
        '
        'TextBox1
        '
        Me.TextBox1.Anchor = CType(((System.Windows.Forms.AnchorStyles.Top Or System.Windows.Forms.AnchorStyles.Left) _
                    Or System.Windows.Forms.AnchorStyles.Right), System.Windows.Forms.AnchorStyles)
        Me.TextBox1.AutoCompleteMode = System.Windows.Forms.AutoCompleteMode.Append
        Me.TextBox1.AutoCompleteSource = System.Windows.Forms.AutoCompleteSource.FileSystemDirectories
        Me.TextBox1.Location = New System.Drawing.Point(12, 25)
        Me.TextBox1.Name = "TextBox1"
        Me.TextBox1.Size = New System.Drawing.Size(434, 20)
        Me.TextBox1.TabIndex = 0
        '
        'Label1
        '
        Me.Label1.AutoSize = True
        Me.Label1.Location = New System.Drawing.Point(9, 9)
        Me.Label1.Name = "Label1"
        Me.Label1.Size = New System.Drawing.Size(110, 13)
        Me.Label1.TabIndex = 1
        Me.Label1.Text = "Количество файлов:"
        '
        'FilesCount
        '
        Me.FilesCount.AutoSize = True
        Me.FilesCount.Location = New System.Drawing.Point(125, 9)
        Me.FilesCount.Name = "FilesCount"
        Me.FilesCount.Size = New System.Drawing.Size(13, 13)
        Me.FilesCount.TabIndex = 2
        Me.FilesCount.Text = "0"
        '
        'DirectoryFiles
        '
        Me.DirectoryFiles.Anchor = CType((((System.Windows.Forms.AnchorStyles.Top Or System.Windows.Forms.AnchorStyles.Bottom) _
                    Or System.Windows.Forms.AnchorStyles.Left) _
                    Or System.Windows.Forms.AnchorStyles.Right), System.Windows.Forms.AnchorStyles)
        Me.DirectoryFiles.FormattingEnabled = True
        Me.DirectoryFiles.IntegralHeight = False
        Me.DirectoryFiles.Location = New System.Drawing.Point(12, 51)
        Me.DirectoryFiles.Name = "irectoryFiles"
        Me.DirectoryFiles.Size = New System.Drawing.Size(434, 453)
        Me.DirectoryFiles.TabIndex = 3
        '
        'Form1
        '
        Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
        Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
        Me.ClientSize = New System.Drawing.Size(458, 516)
        Me.Controls.Add(Me.DirectoryFiles)
        Me.Controls.Add(Me.FilesCount)
        Me.Controls.Add(Me.Label1)
        Me.Controls.Add(Me.TextBox1)
        Me.Name = "Form1"
        Me.Text = "Form1"
        Me.ResumeLayout(False)
        Me.PerformLayout()

    End Sub
    Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
    Friend WithEvents Label1 As System.Windows.Forms.Label
    Friend WithEvents FilesCount As System.Windows.Forms.Label
    Friend WithEvents DirectoryFiles As System.Windows.Forms.ListBox

End Class

Option Strict On

Imports System.IO

Public Class Form1

    Dim Directories As New Dictionary(Of String, List(Of String))
    Dim Files As New Dictionary(Of String, List(Of String))

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim Start = Now
        PreLoad()
        MessageBox.Show(Now.Subtract(Start).ToString)
    End Sub

    Sub PreLoad()
        For Each Drive In DriveInfo.GetDrives
            If Drive.DriveType = DriveType.Fixed Then
                LoadDirectory(Drive.RootDirectory.FullName)
            End If
        Next
    End Sub

    Sub LoadDirectory(ByVal directory As String)
        Try
            Dim SubDirectories = IO.Directory.GetDirectories(directory)
            Dim SubFiles = IO.Directory.GetFiles(directory)

            Dim SubDirectoriesList = New List(Of String)(SubDirectories.Length)
            Dim SubFilesList = New List(Of String)(SubFiles.Length)
            irectories(directory.ToLower) = SubDirectoriesList
            Files(directory.ToLower) = SubFilesList

            For Each SubDirectory In SubDirectories
                SubDirectoriesList.Add(SubDirectory.ToLower)
                LoadDirectory(SubDirectory)
            Next
            For Each File In SubFiles
                SubFilesList.Add(File.ToLower)
            Next
        Catch ex As System.UnauthorizedAccessException
            ' все хорошо
        Catch ex As Exception
            Stop
        End Try
         
    End Sub

    Private Sub TextBox1_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
        Dim Directory As String = Nothing
        If Directories.ContainsKey(TextBox1.Text.ToLower) Then
            irectory = TextBox1.Text.ToLower
        ElseIf Directories.ContainsKey(TextBox1.Text.ToLower + "\" Then
            irectory = TextBox1.Text.ToLower + "\"
        ElseIf TextBox1.Text.Length > 0 AndAlso Directories.ContainsKey(TextBox1.Text.ToLower.Substring(0, TextBox1.Text.Length - 1)) Then
            irectory = TextBox1.Text.ToLower.Substring(0, TextBox1.Text.Length - 1)
        End If

        If Directory IsNot Nothing Then
            Dim ChildFiles As New List(Of String)
            FilesCount.Text = GetContent(Directory, ChildFiles).ToString
            irectoryFiles.DataSource = ChildFiles
        Else
            FilesCount.Text = ""
            irectoryFiles.DataSource = Nothing
        End If
    End Sub

    Function GetContent(ByVal directory As String, ByRef childFiles As List(Of String)) As Integer
        Dim Count = 0
        If Files.ContainsKey(directory) Then
            Dim F = Files(directory)
            Count = F.Count
            If childFiles.Count < 1000 Then
                childFiles.AddRange(F)
            End If
        End If

        If Directories.ContainsKey(directory) Then
            For Each SubDirectory In Directories(directory)
                Count += GetContent(SubDirectory, childFiles)
            Next
        End If
        Return Count
    End Function
End Class

<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
Partial Class Form1
    Inherits System.Windows.Forms.Form

    'Form overrides dispose to clean up the component list.
    <System.Diagnostics.DebuggerNonUserCode()> _
    Protected Overrides Sub Dispose(ByVal disposing As Boolean)
        Try
            If disposing AndAlso components IsNot Nothing Then
                components.Dispose()
            End If
        Finally
            MyBase.Dispose(disposing)
        End Try
    End Sub

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.IContainer

    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.  
    'Do not modify it using the code editor.
    <System.Diagnostics.DebuggerStepThrough()> _
    Private Sub InitializeComponent()
        Me.TextBox1 = New System.Windows.Forms.TextBox
        Me.Label1 = New System.Windows.Forms.Label
        Me.FilesCount = New System.Windows.Forms.Label
        Me.DirectoryFiles = New System.Windows.Forms.ListBox
        Me.SuspendLayout()
        '
        'TextBox1
        '
        Me.TextBox1.Anchor = CType(((System.Windows.Forms.AnchorStyles.Top Or System.Windows.Forms.AnchorStyles.Left) _
                    Or System.Windows.Forms.AnchorStyles.Right), System.Windows.Forms.AnchorStyles)
        Me.TextBox1.AutoCompleteMode = System.Windows.Forms.AutoCompleteMode.Append
        Me.TextBox1.AutoCompleteSource = System.Windows.Forms.AutoCompleteSource.FileSystemDirectories
        Me.TextBox1.Location = New System.Drawing.Point(12, 25)
        Me.TextBox1.Name = "TextBox1"
        Me.TextBox1.Size = New System.Drawing.Size(434, 20)
        Me.TextBox1.TabIndex = 0
        '
        'Label1
        '
        Me.Label1.AutoSize = True
        Me.Label1.Location = New System.Drawing.Point(9, 9)
        Me.Label1.Name = "Label1"
        Me.Label1.Size = New System.Drawing.Size(110, 13)
        Me.Label1.TabIndex = 1
        Me.Label1.Text = "Количество файлов:"
        '
        'FilesCount
        '
        Me.FilesCount.AutoSize = True
        Me.FilesCount.Location = New System.Drawing.Point(125, 9)
        Me.FilesCount.Name = "FilesCount"
        Me.FilesCount.Size = New System.Drawing.Size(13, 13)
        Me.FilesCount.TabIndex = 2
        Me.FilesCount.Text = "0"
        '
        'DirectoryFiles
        '
        Me.DirectoryFiles.Anchor = CType((((System.Windows.Forms.AnchorStyles.Top Or System.Windows.Forms.AnchorStyles.Bottom) _
                    Or System.Windows.Forms.AnchorStyles.Left) _
                    Or System.Windows.Forms.AnchorStyles.Right), System.Windows.Forms.AnchorStyles)
        Me.DirectoryFiles.FormattingEnabled = True
        Me.DirectoryFiles.IntegralHeight = False
        Me.DirectoryFiles.Location = New System.Drawing.Point(12, 51)
        Me.DirectoryFiles.Name = "irectoryFiles"
        Me.DirectoryFiles.Size = New System.Drawing.Size(434, 453)
        Me.DirectoryFiles.TabIndex = 3
        '
        'Form1
        '
        Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
        Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
        Me.ClientSize = New System.Drawing.Size(458, 516)
        Me.Controls.Add(Me.DirectoryFiles)
        Me.Controls.Add(Me.FilesCount)
        Me.Controls.Add(Me.Label1)
        Me.Controls.Add(Me.TextBox1)
        Me.Name = "Form1"
        Me.Text = "Form1"
        Me.ResumeLayout(False)
        Me.PerformLayout()

    End Sub
    Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
    Friend WithEvents Label1 As System.Windows.Forms.Label
    Friend WithEvents FilesCount As System.Windows.Forms.Label
    Friend WithEvents DirectoryFiles As System.Windows.Forms.ListBox

End Class

насчет скорости АПИ по сравнению со встроенными классами, я готов спорить и практика показывает 2-3 кратный прирост скорости!

    Function LoadAllFiles() As List(Of String)
        Dim result As New List(Of String)
        For Each Drive In DriveInfo.GetDrives
            If Drive.DriveType = DriveType.Fixed Then
                LoadFiles(Drive.RootDirectory.FullName, result)
            End If
        Next
        Return result
    End Function

    Sub LoadFiles(ByVal path As String, ByVal files As List(Of String))
        Try
            files.AddRange(IO.Directory.GetFiles(path))
            For Each SubDirectory In IO.Directory.GetDirectories(path)
                LoadFiles(SubDirectory, files)
            Next
        Catch ex As UnauthorizedAccessException
            ' все хорошо
        End Try
    End Sub

    Sub Main()
        Dim start = Now
        Dim Files = LoadAllFiles()
        Console.WriteLine(Now.Subtract(start))
    End Sub

вернитесь к названию поста! человеку может, нужен просто список файлов!

и быстродействие для него не критично!

ReDim Preserve, если тут, собрались такие знатоки коллекций, то может Ника, мне расскажет как в коллекции при вызове метода Add(item) изменяется ее размерность? просто Redim, базару нет, медленно, так как приходиться переопределять весь массив! а Redim Preserve изменяет только его верхнюю границу!

и время потраченное, по сравнению с дисковой операциями можно не считывать!

    Function LoadAllFiles() As String()
        Dim result = New String(0) {}
        For Each Drive In DriveInfo.GetDrives
            If Drive.DriveType = DriveType.Fixed Then
                LoadFiles(Drive.RootDirectory.FullName, result)
            End If
        Next
        Return result
    End Function

    Sub LoadFiles(ByVal path As String, ByRef files As String())
        Try
            Dim CurrentFiles = IO.Directory.GetFiles(path)
            Dim WasFiles = files.Length
            ReDim Preserve files(WasFiles + CurrentFiles.Length - 1)

            For i = 0 To CurrentFiles.Length - 1
                files(i + WasFiles) = CurrentFiles(i)
            Next

            For Each SubDirectory In IO.Directory.GetDirectories(path)
                LoadFiles(SubDirectory, files)
            Next
        Catch ex As UnauthorizedAccessException
            ' все хорошо
        End Try
    End Sub