在VB中，如果检测到某文本文件为非UTF8格式则自动转换为UTF8格式？

检测文本文件格式：

Private Sub Command1_Click()
Dim TempFile As Long
Dim LoadBytes() As Byte
'以二进制读入文件内容
TempFile = FreeFile
filepath = "c:\example.txt"
Open filepath For Binary As #TempFile
ReDim LoadBytes(1 To LOF(TempFile)) As Byte
Get #TempFile, , LoadBytes
Close TempFile

'On Error GoTo NoEncoding
Dim i As Integer, FileCharset As String, strFileHead As String
'从二进制流中分析文件头的编码信息
For i = 1 To 3
strFileHead = strFileHead & Hex(LoadBytes(i))
Next
'判断文件采用了何种编码
If strFileHead = "EFBBBF" Then
'前3个byte如果为 EF BB BF 则表示为 UTF-8编码
FileCharset = "UTF-8"
Else
strFileHead = Left(strFileHead, 4)
If Left(strFileHead, 4) = "FEFF" Then
'此时为 unicode big endian 编码
FileCharset = "Unicode big endian"
ElseIf Left(strFileHead, 4) = "FFFE" Then
'此时为 unicode 编码
FileCharset = "UNICODE"
Else
'否则默认为普通简体中文 GB2312
'你如果知道其它编码的格式还可以继续的分析判断!
FileCharset = "GB2312"
End If
End If
MsgBox filepath & " Text Format is " & FileCharset
End Sub

把下面代码放到模块中，然后调用FileToUTF8即可。声明：此非原创，但记不清作者了，抱歉。
Public Enum Encoding
ANSI
Unicode
UnicodeBigEndian
UTF8
End Enum

Public Function GetEncoding(FileName As String) As Encoding
On Error GoTo Err

Dim fBytes(1) As Byte, freeNum As Integer
freeNum = FreeFile

Open FileName For Binary Access Read As #freeNum
Get #freeNum, , fBytes(0)
Get #freeNum, , fBytes(1)
Close #freeNum

If fBytes(0) = &HFF And fBytes(1) = &HFE Then GetEncoding = Unicode
If fBytes(0) = &HFE And fBytes(1) = &HFF Then GetEncoding = UnicodeBigEndian
If fBytes(0) = &HEF And fBytes(1) = &HBB Then GetEncoding = UTF8
Err:
End Function

Public Sub FileToUTF8(FileName As String)
If GetEncoding(FileName) = UTF8 Then
'如果是UTF8格式，则退出
'否则，进行转换
Exit Sub
End If

Dim fBytes() As Byte, uniString As String, freeNum As Integer
Dim ADO_Stream As Object

freeNum = FreeFile

ReDim fBytes(FileLen(FileName))
Open FileName For Binary Access Read As #freeNum
Get #freeNum, , fBytes
Close #freeNum

uniString = StrConv(fBytes, vbUnicode)

Set ADO_Stream = CreateObject("ADODB.Stream")
With ADO_Stream
.Type = 2
.Mode = 3
.Charset = "UTF-8"
.open
.WriteText uniString
.SaveToFile FileName, 2
.Close
End With
Set ADO_Stream = Nothing
End Sub

进来学习一下