更新第一行文本文件

Question

我的程序本质上是一个小型的银行帐户＆＃34;允许用户将借方和贷记写入帐户（文本文件）。目前，我的程序将允许用户执行此类操作，并在名为＆＃34;显示余额＆＃34;的组合框索引中计算余额。虽然此程序将从余额中减去借方并将余额添加到余额中，但它也应该能够获取现有文件，从中读取余额，保存，等等。

我的问题是当我的程序在文件打开时更新余额时，它不会将余额保存回程序，然后读取余额，显示在＆＃34;显示余额＆＃34; index，然后允许用户继续更新它。

我已经尝试添加StreamReader以在选择show balance index时从文件中读取余额，然后将余额写回文件，但我似乎无法使其正常工作。 这完全是我想要的：该计划目前将把所有的债务和信用写入文件，但我需要一种方式来控制＆＃34;文件中的平衡。我需要阅读资产余额中的平衡（）来自文件，然后可以更改使用的债务和信用，并将其写回到文件，因此可以再次使用。当前平衡设置为默认为0，并且只能在程序打开时进行修改，并且一旦终止并重新启动，平衡将仍然显示为0.这是什么需要固定。  以下是我的代码：

Imports System.IO

Public Class Form1
    Dim tbDollar As String
    Dim tbMemo As String
    Dim fName As String
    Dim creditAmount As String
    Dim debitAMount As String
    Dim Balance As Double
    Dim action As Integer

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Me.Text = "Mike Smith's Bank Account"
        Call LoadData()
        Call MainMenu()
    End Sub

    Private Sub Cb1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles Cb1.SelectedIndexChanged
        action = Cb1.SelectedIndex
        If action = 0 Then
            Call SetUpCredit()
        ElseIf action = 1 Then
            Call SetUpDebit()
        ElseIf action = 2 Then
            Call ShowTransactions()
        ElseIf action = 3 Then
            Call ShowBalance()
        End If
    End Sub

    Private Sub btConfirm_Click(sender As Object, e As EventArgs) Handles btConfirm.Click
        If action = 0 Then
            Call ProcessCredit()
            Balance = Balance + Convert.ToDouble(tbDollar)
        ElseIf action = 1 Then
            Call ProcessDebit()
            Balance = Balance - Convert.ToDouble(tbDollar)
        End If
        Cb1.SelectedIndex = -1
        Tb1.Text = ""
        Tb2.Text = ""
        Lb4.Text = Convert.ToString(Balance)
        Lb1.Visible = False
        Lb2.Visible = False
        Tb1.Visible = False
        Tb2.Visible = False
        ListBox1.Visible = False
        btConfirm.Visible = False
    End Sub

    Private Sub MainMenu()
        btConfirm.Visible = False
        Lb1.Visible = False
        Lb2.Visible = False
        Tb1.Visible = False
        Tb2.Visible = False
        ListBox1.Visible = False
        Lb4.Visible = False
    End Sub

    Private Sub LoadData()
        Dim FileFound = False
        Do Until FileFound = True
            fName = InputBox("Please enter your file path", "Enter your file path")
            If File.Exists(fName) Then
                FileFound = True
            Else
                MessageBox.Show("File not found!", "Error", MessageBoxButtons.OK)
            End If
        Loop
    End Sub

    Private Sub SetUpCredit()
        btConfirm.Visible = True
        Lb1.Visible = True
        Lb2.Visible = True
        Tb1.Visible = True
        Tb2.Visible = True
        ListBox1.Visible = False
        Lb4.Visible = False
        Lb1.Text = "Enter Credit Amount"
        Lb2.Text = "Enter a Memo"
    End Sub

    Private Sub SetUpDebit()
        btConfirm.Visible = True
        Lb1.Visible = True
        Lb2.Visible = True
        Tb1.Visible = True
        Tb2.Visible = True
        ListBox1.Visible = False
        Lb4.Visible = False
        Lb1.Text = "Enter Debit Amount"
        Lb2.Text = "Enter a Memo"
    End Sub

    Private Sub ShowTransactions()
        btConfirm.Visible = False
        Lb1.Visible = False
        Lb2.Visible = False
        Tb1.Visible = False
        Tb2.Visible = False
        ListBox1.Visible = True
        Lb4.Visible = False
        Dim SRObject As StreamReader = New StreamReader(fName)
        Dim ftext As String

        Do While SRObject.Peek() <> -1
            ftext = SRObject.ReadLine()
            If ListBox1.Items.Contains(ftext) Then

            Else
                ListBox1.Items.Add(ftext)
            End If
        Loop

        SRObject.Close()
    End Sub

    Private Sub ShowBalance()
        btConfirm.Visible = False
        Lb1.Visible = False
        Lb2.Visible = False
        Tb1.Visible = False
        Tb2.Visible = False
        ListBox1.Visible = False
        Lb4.Visible = True
        Lb4.Text = "$" + Convert.ToString(Balance)
    End Sub

    Private Sub ProcessCredit()
        tbDollar = Tb1.Text
        tbMemo = Tb2.Text
        Dim SWObject As StreamWriter = New StreamWriter(fName, True)
        SWObject.WriteLine("Credit: " + tbDollar + ", " + tbMemo)
        MessageBox.Show("You credited " + tbDollar + " to your account!", "Success!")
        SWObject.Close()
    End Sub

    Private Sub ProcessDebit()
        tbDollar = Tb1.Text
        tbMemo = Tb2.Text
        Dim SWObject As StreamWriter = New StreamWriter(fName, True)
        SWObject.WriteLine("Debit: " + tbDollar + ", " + tbMemo)
        MessageBox.Show("You debited" + tbDollar + "to your account!", "Success!")
        SWObject.Close()
    End Sub

    Private Sub Tb1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles Tb1.KeyPress
        If Not Char.IsDigit(e.KeyChar) Then e.Handled = True
        If e.KeyChar = "," And Tb1.Text.IndexOf(",") = -1 Then e.Handled = False
        If e.KeyChar = Chr(8) Then e.Handled = False
        If e.KeyChar = "." And Tb1.Text.IndexOf(".") = -1 Then e.Handled = False
        If e.KeyChar = Chr(13) Then Tb2.Focus()
    End Sub
End Class


I believe there should be a streamreader in the show balance sub to read the first line of the file and save it as the balance, and then write the balance back to the user when it is updated, but i cannot seem to get it figured out. Any help would be appreciated.