VB+SQL登录，总显示连接无法执行此操作，它可能在上下文中被关闭 不知道问题出在哪里？求高手指点。。。。。
代码如下：
Dim conn As ADODB.Connection
Dim rs As ADODB.Recordset
Dim Constr As String
Private Sub Form_Load()
Set conn = New ADODB.Connection
Set rs = New ADODB.Recordset
Constr = "Provider=SQLOLEDB.1;Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=IMDB;Data Source=."
conn.Open Constr
End Sub
Private Sub ULdlCmd_Click()
Dim sql As String
If Trim(ULIDTxt.Text) = "" Then
MsgBox "对不起，请输入用户名", vbInformation, App.Title
ULIDTxt.SetFocus
Exit Sub
ElseIf Trim(ULmmTxt.Text) = "" Then
MsgBox "对不起，请输入密码", vbInformation, App.Title
ULmmTxt.SetFocus
End If
sql = "select 用户名，密码 from 用户表 where 用户名='" & ULIDTxt.Text & "'"
rs.Open
If rs.EOF = True Then
MsgBox "用户名不存在！请重新输入", vbInformation, App.Title
ULIDTxt.Text = ""
ULIDTxt.SetFocus
Exit Sub
End If
If ULmmTxt.Text = rs.Fields(1) Then
IBM.Show
Exit Sub
Else
MsgBox "用户密码错误！请重新输入", vbInformation, App.Title
ULmmTxt.Text = ""
ULmmTxt.SetFocus
End If
Unload Userlogin
End Sub
Private Sub ULtcCmd_Click()
If MsgBox("确定要退出吗？", vbQuestion + vbYesNo + vbDefaultButton2, App.Title) = vbYes Then
Unload Me
End If
End Sub