Can I use the same text file in two separate forms within the same project?

Question

Edit: I've found a work around, thanks for all your help :)

I'm working on a computer science project and I'm in the prototype stage right now. I will eventually switch this entire thing to a database once everything for it is sorted on the campus computers but for now I'm using text files. It's written on visual studio using VB (Required by my college). I'm trying to use the same text file in two different forms at different times but I keep getting the same error when I run it, saying that the file is open elsewhere. I assume this is because it reads from that file in the next form but I have made it so that the file isn't even opened until a specific button click on that other window. It reaches this error when I attempt to write data to the file from the first window, I never get to the stage where I read from the file in the next form.

Context:

It's a booking system for a youth hostel, the booking text file is written to, from the booking page and saved. This opens up a booking confirmation page where data is read from the last line of the file and necessary information is taken out (Name, checkin/checkout dates, booking reference etc.) to be inserted into the booking confirmation message so it's sort of tailored to each booking but keeps the same structure. I have a button to "save booking" which would write the data to the file but this is where the error occurs. The other form isn't open, the text file isnt open anywhere else and after writing to the file, it's closed.

Is there a workaround? should I just try using variables to hold the input data to use it in the next form? I'm not too worried about it being perfect because this is just a prototype until my college sorts out its issue with databases but I'd still like it to function the way I want it to.

Thank you :)

From booking page:

Private Sub btnBook_Click(sender As Object, e As EventArgs) Handles btnBook.Click
        Dim NewBooking As Bookings
        Dim errorFlag As Boolean
        Dim bookingID As Integer
        errorFlag = False
        If txtID.Text = "" Or drpNumGuests.Text = "Please Select" Or txtCheckin.Text = "" Or txtCheckout.Text = "" Or txtRoomNo.Text = "" Then
            errorFlag = True
        End If
        If errorFlag = True Then
            MsgBox("Error with data entered, please try again.")
        Else
            Dim sw As New System.IO.StreamWriter("Bookings.txt", True)      'fix
            Dim Booking() As String = File.ReadAllLines("bookings.txt")
            If UBound(Booking) < 0 Then
                bookingID = 0
            Else
                bookingID = Str(Int(Booking(UBound(Booking)).Substring(0, 8)) + 1)      'Automatic BookingID assignment
            End If
            NewBooking.GuestID = LSet(txtID.Text, 9)
            NewBooking.BookingID = LSet(bookingID, 9)
            NewBooking.Name = LSet(txtName.Text, 25)
            NewBooking.GuestNum = LSet(drpNumGuests.Text, 2)
            NewBooking.CheckIn = LSet(txtCheckin.Text, 11)
            NewBooking.CheckOut = LSet(txtCheckout.Text, 11)
            NewBooking.RoomNum = LSet(txtRoomNo.Text, 3)
            NewBooking.Requests = txtRequests.Text

            sw.WriteLine(NewBooking.GuestID & NewBooking.BookingID & NewBooking.Name & NewBooking.GuestNum & NewBooking.CheckIn & NewBooking.CheckOut & NewBooking.RoomNum & NewBooking.Requests)
            FileClose()
            MsgBox("Booking complete")

        End If

    End Sub

    Private Sub btnConfirm_Click(sender As Object, e As EventArgs) Handles btnConfirm.Click
        Booking_Confirmation.Show()
        Me.Hide()

From booking confirmation page:

Private Sub btnGen_Click(sender As Object, e As EventArgs) Handles btnGen.Click
        Dim Bookconfirm() As String = File.ReadAllLines("bookings.txt")
        Dim Name As String
        Dim CheckIn As String
        Dim CheckOut As String
        Dim NumGuests As String
        Dim RoomNum As String
        Dim ID As String
        Dim BookingID As String
        Dim Count As Integer = UBound(Bookconfirm)
        ID = Mid(Bookconfirm(Count), 1, 8)
        BookingID = Mid(Bookconfirm(Count), 10, 8)
        Name = Mid(Bookconfirm(Count), 19, 25)
        CheckIn = Mid(Bookconfirm(Count), 46, 10)
        CheckOut = Mid(Bookconfirm(Count), 57, 10)
        NumGuests = Mid(Bookconfirm(Count), 44, 2)
        RoomNum = Mid(Bookconfirm(Count), 68, 2)

        txtConfirmation.Text = ID & "  Thank you " & Name & " for booking your stay with us. Your booking of " & NumGuests & " has been made for " & CheckIn & "to " & CheckOut & "
                               We look forward to your arrival. Your booking ID is:" & BookingID
End Sub

Answer 1

Here's an alternate version you can try. As suggested by Hursey in the comments, a Using statement will make sure the file is completely closed and released.

bookingID = 0
Dim lastLine As String = File.ReadAllLines("bookings.txt").LastOrDefault()
If Not IsNothing(lastLine) Then
    bookingID = Str(Int(lastLine.Substring(0, 8)) + 1) 'Automatic BookingID assignment
End If

NewBooking.GuestID = LSet(txtID.Text, 9)
NewBooking.BookingID = LSet(bookingID, 9)
NewBooking.Name = LSet(txtName.Text, 25)
NewBooking.GuestNum = LSet(drpNumGuests.Text, 2)
NewBooking.CheckIn = LSet(txtCheckin.Text, 11)
NewBooking.CheckOut = LSet(txtCheckout.Text, 11)
NewBooking.RoomNum = LSet(txtRoomNo.Text, 3)
NewBooking.Requests = txtRequests.Text

Using sw As New System.IO.StreamWriter("Bookings.txt", True)
    sw.WriteLine(NewBooking.GuestID & NewBooking.BookingID & NewBooking.Name & NewBooking.GuestNum & NewBooking.CheckIn & NewBooking.CheckOut & NewBooking.RoomNum & NewBooking.Requests)
End Using

MsgBox("Booking complete")

If all of the information is already in NewBooking then either PASS that to the secondary form, or simply move it's declaration out to FORM level so that it's accessible. Then you won't need to read the file again to retrieve the information you literally just had?...