如何使文本文件在一定时间后使用计时器自动删除

Question

我正在做一个使用文本文件来点餐和查看餐厅订单的项目。我希望使用计时器自动删除一个小时后保存订单详细信息的文本文件。我其余的代码都可以正常工作，只是自动计时器不起作用。

Public Class frmOrderSummary
Dim strOrderName As String = ""
Private Sub frmSummary_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    'calling display order sub
    Call DisplayOrder()
    timerOrder.Start()
    Dim FileToDelete As String
    timerOrder.Start()
    FileToDelete = (txtOrderNum.Text & ".txt")
    If System.IO.File.Exists(FileToDelete) = True And timerOrder.Interval = 400 Then
        System.IO.File.Delete(FileToDelete)
        MessageBox.Show("File Deleted")
    End If
End Sub
Private Sub lstOrders_SelectedIndexChanged(sender As Object, e As EventArgs) Handles lstOrders.SelectedIndexChanged
    'items selected from listbox will appear in textbox below
    strOrderName = lstOrders.Text
    txtOrderNum.Text = lstOrders.Text

End Sub
Sub DisplayOrder()
    'adding items from OrderNums.txt to listbox
    lstOrders.Items.Clear()
    If IO.File.Exists("OrderNums.txt") Then
        Dim query = From OrderNum In IO.File.ReadAllLines("OrderNums.txt")
                    Order By OrderNum Ascending
                    Select OrderNum
        For Each OrderNum In query
            lstOrders.Items.Add(OrderNum)

        Next
    End If
End Sub

Private Sub btnDisplay_Click(sender As Object, e As EventArgs) Handles btnDisplay.Click
    'using textfile to assign stored data to specific textboxes using arrays
    If (txtOrderNum.Text & ".txt" <> "") And IO.File.Exists(txtOrderNum.Text & ".txt") Then
        Dim query = From line In IO.File.ReadAllLines(txtOrderNum.Text & ".txt")

        Dim name = query(0).Split(","c)(0)
        Dim surname = query(0).Split(",")(1)
        Dim address = query(0).Split(","c)(2)
        Dim phonenum = query(0).Split(","c)(3)
        Dim method = query(0).Split(","c)(4)

        txtName.Text = name
        txtSurname.Text = surname
        txtAddress.Text = address
        txtPhoneNum.Text = phonenum
        txtMethod.Text = method

        Dim cellvalue(20) As String
        Dim OrderID As String
        OrderID = txtOrderNum.Text

        Dim lines = IO.File.ReadAllLines(OrderID & ".txt")
        For index = 1 To lines.Length - 1
            Dim cells = lines(index).Split(","c)
            dgvOutput.Rows.Add(cells)
        Next
    End If
End Sub