vb程序改写方法。

1。经常出现的写法

在VB中实现对数据库的访问，我们可能会通过一个全局函数来实现，例如以下的代码：

Public Function DBSqlOpen(strName As String, strPWD As String, _

strIP As String, strDatabase As String) As ADODB.Connection

'PurPose: 连接SQl数据库

'Accepts:

' strName-------登陆服务器用户名

' strPWD--------登陆服务器密码

' strIP---------服务器地址

' strDatabase---数据库名

'Return: 连接对象

Dim madocon As ADODB.Connection '///////////////////////////////

Set madocon = New ADODB.Connection

madocon.ConnectionString = "Provider=SQLOLEDB.1;Persist Security Info=False;User ID=" _

& strName & ";pwd=" & strPWD & ";Initial Catalog=" & strDatabase & ";Data Source=" & strIP & ""

madocon.Open

Set DBSqlOpen = madocon

End Function

然后在其它地方要用到Ado连接的时候就通过该函数来返回。比如:

Private Sub Form_Load()

Set rs = New ADODB.Recordset

rs.CursorType = adOpenKeyset

rs.LockType = adLockPessimistic

rs.ActiveConnection = DBSqlOpen(strLocalName, strLocalPwd, "(local)", strLocalDb)

........

End Sub

程序中如果采用这种方式来实现连接数据库，效率非常的低下。你每用到一次DBSqlOpen这个全局函数，全局函数里面声明的 AdoDB.Connection就会Open一次，假如你的程序频繁调用这个全局函数，可想而之程序的效率将会多么的低下。如何避免这种设计方式呢？我 们采用下面的方式。

2.改进的写法

假如我们设计一个类来实现数据库访问就会避免这样的问题。具体代码如下：

Private m_adoConn As New ADODB.Connection

Private m_adoRecordSet As New ADODB.Recordset

Public Function DBInit()

Set m_adoConn = Nothing

Set m_adoRecordSet = Nothing

End Function

Public Function DBEnd()

m_adoRecordSet.Close

m_adoConn.Close

Set m_adoRecordSet = Nothing

Set m_conn = Nothing

End Function

Public Function DBSqlOpen(strName As String, strPWD As String, _

strIP As String, strDatabase As String)

m_adoConn.ConnectionString = "Provider=SQLOLEDB.1;Persist Security Info=False;User ID=" _

& strName & ";pwd=" & strPWD & ";Initial Catalog=" & strDatabase & ";Data Source=" & strIP & ""

m_adoConn.ConnectionTimeout = 5

m_adoConn.Open

End Function

Public Function DBGetConn() As ADODB.Connection

DBGetConn = m_adoConn

End Function

我们在模块里面可以声明一个Public m_DBClass As DBClass来实现对数据库的访问。

Private Sub Command1_Click()

Dim rs1 As ADODB.Recordset

rs1.ActiveConnection = m_DBClass.DBGetConn

End Sub

Private Sub Form_Load()

Dim strName As String

Dim strPWD As String

Dim strIP As String

Dim strDatabase As String

strName = "sa"

strPWD = ""

strIP = "192.168.0.37"

strDatabase = ""

m_DBClass.DBInit

m_DBClass.DBSqlOpen strName, strPWD, strIP, strDatabase

End Sub

Private Sub Form_Unload(Cancel As Integer)

m_DBClass.DBEnd

End Sub

每一次要用到数据库连接的时候我们就通过类里面的DBGetConn方法来返回一个ADODB.Connection。