Как правильно открыть TXT файл для чтения, например чтобы запихнуть в TextBox или просто загрузить в массив строк

    With S
        .Type = 2 'или 1 или вообще закомментируй строку
        .Charset = "UTF-8"
        .Open
        .WriteText TextContent
        .Position = 0
        .SaveToFile FilePath, 2 'adSaveCreateOverWrite
        .Close
    End With

Public Sub WriteToTextFileUTF8(FilePath As String, TextContent As String)
    Dim S As Object
    Set S = CreateObject("ADODB.Stream")
    
    With S
        .Type = 2
        .Charset = "UTF-8"
        .Open
        .WriteText TextContent
        .Position = 0
        .SaveToFile FilePath, 2
        .Close
    End With
End Sub

    Dim str As String
    Dim arr() As Byte
    Dim hFile As Long
    Dim nOutputByteLen As Long
    
    str = "ля ля ля тополя"
    
    If Len(str) > 0 Then
        nOutputByteLen = WideCharToMultiByte(CP_UTF8, 0&, StrPtr(str), Len(str), 0&, 0&, 0&, 0&)
        
        If nOutputByteLen > 0 Then
            ReDim arr(nOutputByteLen + 2)
            WideCharToMultiByte CP_UTF8, 0&, StrPtr(str), Len(str), VarPtr(arr(3)), nOutputByteLen, 0&, 0&
            
            arr(0) = &HEF
            arr(1) = &HBB
            arr(2) = &HBF
            
            hFile = CreateFile(StrPtr(AppPath & "\имя файла.txt"), GENERIC_WRITE, FILE_SHARE_READ, ByVal 0&, CREATE_ALWAYS, FILE_ATTRIBUTE_ARCHIVE, 0)
            
            If hFile <> INVALID_HANDLE_VALUE Then
                WriteFile hFile, VarPtr(arr(0)), nOutputByteLen + 3, 0, ByVal 0&
                CloseHandle hFile
            End If
        End If
    End If

    With S
        .Charset = "UTF-8"
        .Open
        .WriteText TextContent
        .SaveToFile FilePath, 2
        .Close
    End With

Private Declare Function ReadFile Lib "kernel32" (ByVal hFile As Long, ByVal lpBuffer As Long, ByVal nNumberOfBytesToRead As Long, lpNumberOfBytesRead As Long, ByVal lpOverlapped As Any) As Long
Private Declare Function GetFileSize Lib "kernel32" (ByVal hFile As Long, lpFileSizeHigh As Long) As Long
Private Declare Sub PutMem4 Lib "msvbvm60" (ByVal Ptr As Long, ByVal Value As Long)
Private Declare Function SysAllocStringByteLen Lib "oleaut32" (ByVal olestr As Long, ByVal BLen As Long) As Long
Private Declare Function SysAllocStringLen Lib "oleaut32" (ByVal olestr As Long, ByVal BLen As Long) As Long
Private Declare Function MultiByteToWideChar Lib "kernel32" (ByVal CodePage As Long, ByVal dwFlags As Long, ByVal lpMultiByteStr As Long, ByVal cbMultiByte As Long, ByVal lpWideCharStr As Long, ByVal cchWideChar As Long) As Long
Public Declare Function CreateFile Lib "kernel32" Alias "CreateFileW" (ByVal lpFileName As Long, ByVal dwDesiredAccess As Long, ByVal dwShareMode As Long, lpSecurityAttributes As Any, ByVal dwCreationDisposition As Long, ByVal dwFlagsAndAttributes As Long, ByVal hTemplateFile As Long) As Long
Public Declare Function WriteFile Lib "kernel32" (ByVal hFile As Long, ByVal lpBuffer As Long, ByVal nNumberOfBytesToWrite As Long, ByRef lpNumberOfBytesWritten As Long, ByVal lpOverlapped As Any) As Long
Public Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long
 
 
Private Const OPEN_EXISTING As Long = 3
Private Const GENERIC_READ As Long = &H80000000
Private Const CP_UTF8 As Long = 65001
Public Const GENERIC_WRITE As Long = &H40000000
Public Const FILE_SHARE_READ = &H1
Public Const CREATE_ALWAYS = 2
Public Const FILE_ATTRIBUTE_ARCHIVE = &H20
Public Const INVALID_HANDLE_VALUE As Long = -1
 
 
Dim hFile As Long
    Dim stringbuffer As String
    Dim stringbuffer2 As String
    Dim numread As Long
    Dim FileSize As Long
    Dim nOutputCharLen As Long
 
' Загрузка списка
    hFile = CreateFile(StrPtr(FileName), GENERIC_READ, FILE_SHARE_READ, ByVal 0&, OPEN_EXISTING, FILE_ATTRIBUTE_ARCHIVE, 0)
    
    If hFile <> INVALID_HANDLE_VALUE Then
        ' Получить размер файла
        FileSize = GetFileSize(hFile, ByVal 0&) ' Этот метод только до 2Гб
        
        If FileSize > 0 Then
            PutMem4 VarPtr(stringbuffer), SysAllocStringByteLen(0&, FileSize) ' Мгновенно выделить память для строки
            ReadFile hFile, StrPtr(stringbuffer), FileSize, numread, ByVal 0& ' Прочитать файл, ровно столько байтов, сколько нужно
            
            nOutputCharLen = MultiByteToWideChar(CP_UTF8, 0&, StrPtr(stringbuffer), FileSize, 0&, 0&)
            If nOutputCharLen > 0 Then
                PutMem4 VarPtr(stringbuffer2), SysAllocStringLen(0&, nOutputCharLen)
                MultiByteToWideChar CP_UTF8, 0&, StrPtr(stringbuffer), FileSize, StrPtr(stringbuffer2), nOutputCharLen ' Преобразовать кодировки
                
                ' stringbuffer2 содержит текст файла, его можно при желании преобразовать в массив через Split или QuickSplit
                
                If MidB$(stringbuffer, 1, 3) = ChrW(&HBBEF) & ChrB(&HBF) Then ' Если есть запись BOM
                    QuickSplit2 MidB$(stringbuffer2, 3), DataList, vbNewLine ' Быстро преобразовать строку в массив
                Else
                    QuickSplit2 stringbuffer2, DataList, vbNewLine
                End If
               
            End If
        End If
        
        CloseHandle hFile
    End If

Option Explicit
Private Declare Function ReadFile Lib "kernel32" (ByVal hFile As Long, ByVal lpBuffer As Long, ByVal nNumberOfBytesToRead As Long, lpNumberOfBytesRead As Long, ByVal lpOverlapped As Any) As Long
Private Declare Function GetFileSize Lib "kernel32" (ByVal hFile As Long, lpFileSizeHigh As Long) As Long
Private Declare Sub PutMem4 Lib "msvbvm60" (ByVal Ptr As Long, ByVal Value As Long)
Private Declare Function SysAllocStringByteLen Lib "oleaut32" (ByVal olestr As Long, ByVal BLen As Long) As Long
Private Declare Function SysAllocStringLen Lib "oleaut32" (ByVal olestr As Long, ByVal BLen As Long) As Long
Private Declare Function MultiByteToWideChar Lib "kernel32" (ByVal CodePage As Long, ByVal dwFlags As Long, ByVal lpMultiByteStr As Long, ByVal cbMultiByte As Long, ByVal lpWideCharStr As Long, ByVal cchWideChar As Long) As Long
Private Declare Function CreateFile Lib "kernel32" Alias "CreateFileW" (ByVal lpFileName As Long, ByVal dwDesiredAccess As Long, ByVal dwShareMode As Long, lpSecurityAttributes As Any, ByVal dwCreationDisposition As Long, ByVal dwFlagsAndAttributes As Long, ByVal hTemplateFile As Long) As Long
Private Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long
 
Private Const OPEN_EXISTING As Long = 3
Private Const GENERIC_READ As Long = &H80000000
Private Const CP_UTF8 As Long = 65001
Private Const GENERIC_WRITE As Long = &H40000000
Private Const FILE_SHARE_READ = &H1
Private Const CREATE_ALWAYS = 2
Private Const FILE_ATTRIBUTE_ARCHIVE = &H20
Private Const INVALID_HANDLE_VALUE As Long = -1
 
Public Function ReadFromTextFileUTF8(ByVal FileName As String) As String
    Dim hFile As Long
    Dim stringbuffer As String
    Dim numread As Long
    Dim FileSize As Long
    Dim nOutputCharLen As Long
    Dim lpMultiByteStr As Long
    
    hFile = CreateFile(StrPtr(FileName), GENERIC_READ, FILE_SHARE_READ, ByVal 0&, OPEN_EXISTING, FILE_ATTRIBUTE_ARCHIVE, 0)
    
    If hFile <> INVALID_HANDLE_VALUE Then
        FileSize = GetFileSize(hFile, ByVal 0&) ' Этот метод только до 2Гб
        
        If FileSize > 0 Then
            PutMem4 VarPtr(stringbuffer), SysAllocStringByteLen(0&, FileSize) ' Мгновенно выделить память для строки
            
            If ReadFile(hFile, StrPtr(stringbuffer), FileSize, numread, ByVal 0&) > 0 Then
                If MidB$(stringbuffer, 1, 3) = ChrW(&HBBEF) & ChrB(&HBF) Then ' Если есть запись BOM
                    lpMultiByteStr = StrPtr(stringbuffer) + 3
                Else
                    lpMultiByteStr = StrPtr(stringbuffer)
                End If
                
                nOutputCharLen = MultiByteToWideChar(CP_UTF8, 0&, lpMultiByteStr, FileSize, 0&, 0&)
                If nOutputCharLen > 0 Then
                    PutMem4 VarPtr(ReadFromTextFileUTF8), SysAllocStringLen(0&, nOutputCharLen)
                    MultiByteToWideChar CP_UTF8, 0&, lpMultiByteStr, FileSize, StrPtr(ReadFromTextFileUTF8), nOutputCharLen ' Преобразовать кодировки
                End If
            End If
        End If
        
        CloseHandle hFile
    End If
End Function

stringbuffer = String(FileSize, vbNullString)

Option Explicit
Private Declare Function GetTickCount Lib "kernel32" () As Long
 
Private Sub Command1_Click()
    Dim tick As Long
    Dim str As String
    
    tick = GetTickCount
    
    str = String$(100000000, vbNullChar) ' Примерно 100 Мб строки данных
    
    Print GetTickCount - tick ' Примерно 125 млск на четырёхядерном мощном процессоре (на слабых машинах может быть куда больше млск)
End Sub

Option Explicit
Private Declare Function GetTickCount Lib "kernel32" () As Long
Private Declare Sub PutMem4 Lib "msvbvm60" (ByVal Ptr As Long, ByVal Value As Long)
Private Declare Function SysAllocStringLen Lib "oleaut32" (ByVal olestr As Long, ByVal BLen As Long) As Long
 
' А теперь попробуем тоже самое с помощью API-функций
Private Sub Command2_Click()
    Dim tick As Long
    Dim str As String
    
    tick = GetTickCount
    
    PutMem4 VarPtr(str), SysAllocStringLen(0&, 100000000) ' Мгновенно выделить память для строки
    
    Print GetTickCount - tick ' 0 млск - абсолютно гновенно!
End Sub

str = Space$(count)

Dim tick As Long
    Dim str As String
    
    tick = GetTickCount
    
    str = Space$(100000000) ' Примерно 200 Мб строки данных (по два байта на один символ)
    
    Print GetTickCount - tick ' Примерно 125 млск на четырёхядерном мощном процессоре (на слабых машинах может быть куда больше млск)