vb 中连接无法用于执行此操作，在此上下文中它可能已被关闭或无效

Option Explicit
Public cn As New ADODB.Connection
Public rst As New ADODB.Recordset

Dim xian As Integer


Private Sub CmdExit_Click()
Unload Me
End Sub

Private Sub Command1_Click()
If xian <> 1 Then
  MsgBox "请先点击显示", 0 + 48, "错误提示"
  Else
  rst.MoveNext
  If rst.EOF = True Then
  rst.MoveFirst
 End If
  
  Text1.Text = rst.Fields("宿舍号")
  Text2.Text = rst.Fields("物品")
  Text3.Text = rst.Fields("提交日期")
  Text4.Text = rst.Fields("解决日期")
  Text5.Text = rst.Fields("报修原因")
   
   
 End If
End Sub

Private Sub cmd_Click()
  xian = 1
  Dim ssql As String
  ssql = "select * from 学生报修登记表 order by 宿舍号"
  Set rst = Nothing
  rst.Open ssql, cn, adOpenKeyset, adLockOptimistic
  Set DataGrid1.DataSource = rst
  DataGrid1.Refresh
  Text1.Text = rst.Fields("宿舍号")
  Text2.Text = rst.Fields("物品")
  Text3.Text = rst.Fields("提交日期")
  Text4.Text = rst.Fields("解决日期")
  Text5.Text = rst.Fields("报修原因")
   
End Sub

Private Sub CmdAdd_Click()
  Dim inte As String
  Dim SQLstr As String
  If xian <> 1 Then
  MsgBox "请先点击显示", 0 + 48, "错误提示"
  Else
  If Text1.Text = "" Then
  MsgBox "宿舍号不能为空", 0 + 48, "错误提示"
  Else
  inte = "select * from 学生报修登记表 where 宿舍号='" & Text1.Text & "'"
  Set rst = Nothing
  rst.Open inte, cn, adOpenKeyset, adLockOptimistic
  DataGrid1.Refresh
  If rst.RecordCount > 0 Then
  MsgBox "宿舍号重复，插入错误", 0 + 48, "错误提示"
   
  Else
  SQLstr = "Insert into 报修表 (宿舍号,物品,提交日期,解决日期,报修原因) values" _
  & "('" & Text1.Text & "'" _
  & ",'" & Text2.Text & "'" _
  & ",'" & Text3.Text & "'" _
  & ",'" & Text4.Text & "'" _
  & ",'" & Text5.Text & "')"
  Set rst = Nothing
  rst.Open SQLstr, cn, adOpenKeyset, adLockOptimistic
  MsgBox "添加成功！"
  Call cmd_Click
  End If
  End If
  End If
  xian = 1
  Dim ssql As String
  ssql = "select * from 学生报修登记表 order by 宿舍号"
  Set rst = Nothing
  rst.Open ssql, cn, adOpenKeyset, adLockOptimistic
  Set DataGrid1.DataSource = rst
  DataGrid1.Refresh
   
  Text1.Text = rst.Fields("宿舍号")
  Text2.Text = rst.Fields("物品")
  Text3.Text = rst.Fields("提交日期")
  Text4.Text = rst.Fields("解决日期")
  Text5.Text = rst.Fields("报修原因")
   
End Sub
Private Sub Command2_Click()
  If xian <> 1 Then
  MsgBox "请先点击显示", 0 + 48, "错误提示"
  Else
  rst.MovePrevious
  If rst.BOF = True Then
  rst.MoveLast
  End If
  Text1.Text = rst.Fields("宿舍号")
  Text2.Text = rst.Fields("物品")
  Text3.Text = rst.Fields("提交日期")
  Text4.Text = rst.Fields("解决日期")
  Text5.Text = rst.Fields("报修原因")
   
  End If
   
End Sub
Private Sub Cmddelete_Click()
  If xian <> 1 Then
  MsgBox "请先点击显示", 0 + 48, "错误提示"
  Else
  If Text1.Text = "" Then
  MsgBox "宿舍号不能为空", 0 + 48, "错误提示"
  Else
  If MsgBox(" 确定删除?", 1 + 32, "删除提示") = 1 Then
  Dim SQLstr2 As String
  SQLstr2 = "delete from 学生报修登记表 where 宿舍号 = " & "'" & Text1.Text & "'"
  Set rst = Nothing
  rst.Open SQLstr2, cn, adOpenKeyset, adLockOptimistic
  MsgBox "删除成功！"
  Call cmd_Click
  End If
  End If
  End If
   
End Sub
Private Sub CmdModify_Click()
  Dim SQLstr3 As String
  If xian <> 1 Then
  MsgBox "请先点击显示", 0 + 48, "错误提示"
  Else
  If Text1.Text = "" Then
  MsgBox "宿舍号不能为空", 0 + 48, "错误提示"
   
  Else
  SQLstr3 = "update 学生报修登记表 set " _
  & "物品= " & "'" & Text2.Text & "'" _
  & "," & "提交日期= " & "'" & Text3.Text & "'" _
  & "," & "报修日期= " & "'" & Text4.Text & "'" _
  & "," & "报修原因= " & Text5.Text _
  & " where 宿舍号 =" & "'" & Text1.Text & "'"
  Set rst = Nothing
  rst.Open SQLstr3, cn, adOpenKeyset, adLockOptimistic
  MsgBox "修改成功！"
  Call cmd_Click
  End If
  End If
   
End Sub


vb 中连接无法用于执行此操作，在此上下文中它可能已被关闭或无效

与数据库没有连接吧