使用ADO控件可以方便的在VB6中访问ODBC数据库，但是通过直接放置ADODS控件来获得ADO的数据连接比较麻烦，我们可以在VB工程中创建一个公共数据模块，将ADO控件的初始化、建立连接、关闭连接等操作都写到函数中，这样就可以在工程的其他模块中共享调用这个ADO连接。
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一次完整的ADO调用操作分为如下几个步骤：
打开ADO到数据库的连接，初始化ADO RECORDSET集。
通过写入SQL语句执行查询并返回查询结果RECORDSET集；或者可以通过写入SQL语句执行相应数据库操作。
释放RECORDSET集，关闭数据库连接。
需要注意的是，每个动态创建的ADO同时只能被一个过程调用，如果需要进行多表并行操作，可能需要在公共数据模块中建立多个动态ADO。
下面是相关的代码：
'-----------------------------------------------------------------
'如下代码保存在名为my.bas的工程模块中
Public CONN As Adodb.Connection '定义ADO CONNECTION对象
Public RS As Adodb.Recordset '定义ADO RECORDSET对象
'****************************
'打开数据库连接
'****************************
Function ConnOpen()
Dim ASTR As String
Set CONN = New Adodb.Connection
ASTR = GetDatabasePath 'MDB文件数据库路径
CONN.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" ASTR ";Persist Security Info=False"
'本例的ODBC连接为JET4.0的直接到MDB文件的连接，如果使用ODBC数据源可以使用如下CONNECTION串：
'Provider=MSDASQL.1;Password="";Persist Security Info=True;Data Source=数据源名称;Initial Catalog=数据表库名称
Option Explicit
'mTextUTF.bas
'模块：UTF文本文件访问
'作者：zyl910
'版本：1.0
'日期：2006-1-23
'== 说明 ===================================================
'支持Unicode编码的文本文件读写。暂时支持ANSI、UTF-8、UTF-16LE、UTF-16BE这几种编码文本
'== 更新记录 ===============================================
'[V1.0] 2006-1-23
'1.支持最常见的ANSI、UTF-8、UTF-16LE、UTF-16BE这几种编码文本
'## 编译预处理常数 #########################################
'== 全局常数 ===============================================
'IncludeAPILib：引用了API库，此时不需要手动写API声明
'## API ####################################################
#If IncludeAPILib = 0 Then
'== File ===================================================
Private Declare Function CreateFile Lib "kernel32" Alias "CreateFileA" (ByVal lpFileName As String, ByVal dwDesiredAccess As Long, ByVal dwShareMode As Long, ByVal lpSecurityAttributes As Long, 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 Declare Function ReadFile Lib "kernel32" (ByVal hFile As Long, lpBuffer As Any, ByVal nNumberOfBytesToRead As Long, lpNumberOfBytesRead As Long, ByVal lpOverlapped As Long) As Long
Private Declare Function WriteFile Lib "kernel32" (ByVal hFile As Long, lpBuffer As Any, ByVal nNumberOfBytesToWrite As Long, lpNumberOfBytesWritten As Long, ByVal lpOverlapped As Long) As Long
Private Declare Function GetFileSize Lib "kernel32" (ByVal hFile As Long, lpFileSizeHigh As Long) As Long
Private Declare Function SetFilePointer Lib "kernel32" (ByVal hFile As Long, ByVal lDistanceToMove As Long, lpDistanceToMoveHigh As Long, ByVal dwMoveMethod As Long) As Long
Private Const INVALID_HANDLE_VALUE = -1
Private Const GENERIC_READ = H80000000
Private Const GENERIC_WRITE = H40000000
Private Const FILE_SHARE_READ = H1
Private Const FILE_SHARE_WRITE = H2
Private Const Create_NEW = 1
Private Const Create_ALWAYS = 2
Private Const OPEN_EXISTING = 3
Private Const OPEN_ALWAYS = 4
Private Const TRUNCATE_EXISTING = 5
Private Const FILE_ATTRIBUTE_NORMAL = H80
Private Const FILE_BEGIN = 0
Private Const FILE_CURRENT = 1
Private Const FILE_END = 2
'== Unicode ================================================
Private Declare Function MultiByteToWideChar Lib "kernel32" (ByVal CodePage As Long, ByVal dwFlags As Long, ByRef lpMultiByteStr As Any, ByVal cchMultiByte As Long, ByRef lpWideCharStr As Any, ByVal cchWideChar As Long) As Long
Private Declare Function WideCharToMultiByte Lib "kernel32" (ByVal CodePage As Long, ByVal dwFlags As Long, ByRef lpWideCharStr As Any, ByVal cchWideChar As Long, ByRef lpMultiByteStr As Any, ByVal cchMultiByte As Long, ByRef lpDefaultChar As Any, ByVal lpUsedDefaultChar As Long) As Long
Private Const CP_UTF8 As Long = 65001
#End If
'###########################################################
'Unicode编码格式
Public Enum UnicodeEncodeFormat
UEF_ANSI = 0 'ANSI+DBCS
UEF_UTF8 'UTF-8
UEF_UTF16LE 'UTF-16LE
UEF_UTF16BE 'UTF-16BE
UEF_UTF32LE 'UTF-32LE
UEF_UTF32BE 'UTF-32BE
UEF_Auto = -1 '自动识别编码
'隐藏项目
[_UEF_Min] = UEF_ANSI
[_UEF_Max] = UEF_UTF32BE
End Enum
'ANSI+DBCS方式的文本所使用的代码页。默认为0，表示使用系统当前代码页。可以利用该参数实现读取其他代码编码的文本，比如想在 简体中文平台下 读取 繁体中文平台生成的txt，就将它设为950
Public UEFCodePage As Long
'判断BOM
'返回值：BOM所占字节
'dwFirst：[in]文件最开始的4个字节
'fmt：[out]返回编码类型
Public Function UEFCheckBOM(ByVal dwFirst As Long, ByRef fmt As UnicodeEncodeFormat) As Long
If dwFirst = HFEFF Then
fmt = UEF_UTF32LE
UEFCheckBOM = 4
ElseIf dwFirst = HFFFE0000 Then
fmt = UEF_UTF32BE
UEFCheckBOM = 4
ElseIf (dwFirst And HFFFF) = HFEFF Then
fmt = UEF_UTF16LE
UEFCheckBOM = 2
ElseIf (dwFirst And HFFFF) = HFFFE Then
fmt = UEF_UTF16BE
UEFCheckBOM = 2
ElseIf (dwFirst And HFFFFFF) = HBFBBEF Then
fmt = UEF_UTF8
UEFCheckBOM = 3
Else
fmt = UEF_ANSI
UEFCheckBOM = 0
End If
End Function
'生成BOM
'返回值：BOM所占字节
'fmt：[in]编码类型
'dwFirst：[out]文件最开始的4个字节
Public Function UEFMakeBOM(ByVal fmt As UnicodeEncodeFormat, ByRef dwFirst As Long) As Long
Select Case fmt
Case UEF_UTF8
dwFirst = HBFBBEF
UEFMakeBOM = 3
Case UEF_UTF16LE
dwFirst = HFEFF
UEFMakeBOM = 2
Case UEF_UTF16BE
dwFirst = HFFFE
UEFMakeBOM = 2
Case UEF_UTF32LE
dwFirst = HFEFF
UEFMakeBOM = 4
Case UEF_UTF32BE
dwFirst = HFFFE0000
UEFMakeBOM = 4
Case Else
dwFirst = 0
UEFMakeBOM = 0
End Select
End Function
'判断文本文件的编码类型
'返回值：编码类型。文件无法打开时，返回UEF_Auto
'FileName：文件名
Public Function UEFCheckTextFileFormat(ByVal FileName As String) As UnicodeEncodeFormat
Dim hFile As Long
Dim dwFirst As Long
Dim nNumRead As Long
'打开文件
hFile = CreateFile(FileName, GENERIC_READ, FILE_SHARE_READ Or FILE_SHARE_WRITE, ByVal 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, ByVal 0)
If INVALID_HANDLE_VALUE = hFile Then '文件无法打开
UEFCheckTextFileFormat = UEF_Auto
Exit Function
End If
'判断BOM
dwFirst = 0
Call ReadFile(hFile, dwFirst, 4, nNumRead, ByVal 0)
nNumRead = UEFCheckBOM(dwFirst, UEFCheckTextFileFormat)
'Debug.Print nNumRead
'关闭文件
Call CloseHandle(hFile)
End Function
'读取文本文件
'返回值：读取的文本。返回vbNullString表示文件无法打开
'FileName：[in]文件名
'fmt：[in,out]使用何种文本编码格式来读取文本。为UEF_Auto时表示自动判断，且在fmt参数返回文本所用编码格式
Public Function UEFLoadTextFile(ByVal FileName As String, Optional ByRef fmt As UnicodeEncodeFormat = UEF_Auto) As String
Dim hFile As Long
Dim nFileSize As Long
Dim nNumRead As Long
Dim dwFirst As Long
Dim CurFmt As UnicodeEncodeFormat
Dim cbBOM As Long
Dim cbTextData As Long
Dim CurCP As Long
Dim byBuf() As Byte
Dim cchStr As Long
Dim I As Long
Dim byTemp As Byte
'判断fmt范围
If fmt UEF_Auto Then
If fmt [_UEF_Min] Or fmt [_UEF_Max] Then
GoTo FunEnd
End If
End If
'打开文件
hFile = CreateFile(FileName, GENERIC_READ, FILE_SHARE_READ Or FILE_SHARE_WRITE, ByVal 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, ByVal 0)
If INVALID_HANDLE_VALUE = hFile Then '文件无法打开
GoTo FunEnd
End If
'判断文件大小
nFileSize = GetFileSize(hFile, nNumRead)
If nNumRead 0 Then '超过4GB
GoTo FreeHandle
End If
If nFileSize 0 Then '超过2GB
GoTo FreeHandle
End If
'判断BOM
dwFirst = 0
Call ReadFile(hFile, dwFirst, 4, nNumRead, ByVal 0)
cbBOM = UEFCheckBOM(dwFirst, CurFmt)
'恢复文件指针
If fmt = UEF_Auto Then '自动判断
fmt = CurFmt
'cbBOM = cbBOM
Else '手动设置编码
If fmt = CurFmt Then '若编码相同，则忽略BOM标记
'cbBOM = cbBOM
Else '编码不同，那么都是数据
cbBOM = 0
End If
End If
Call SetFilePointer(hFile, cbBOM, ByVal 0, FILE_BEGIN)
cbTextData = nFileSize - cbBOM
'读取数据
UEFLoadTextFile = ""
Select Case fmt
Case UEF_ANSI, UEF_UTF8
'判断应使用的CodePage
CurCP = IIf(fmt = UEF_UTF8, CP_UTF8, UEFCodePage)
.bas是模块, 不能直接运行, 里面应该有一些全局的函数. 在工程上点右键--添加--模块, 然后选择bas文件就可以导入这个模块了
窗体中的过程作用域只在该窗体内有效，你要定义全局过程必须在类模块或模块下定义的
