將文本加載到列表框中

Question

我需要實現的主要目標是使用戶輸入的詳細信息（例如使用的分鐘數和總費用等）在一個列表中顯示給用戶，一旦所有框都有已被填寫。然後，他們可以將該框/列表框中的文本保存到PC上的txt文件中。

這幾乎是我所需要做的。我似乎無法做到這一點，並不知道我該怎麼做。這是迄今爲止我所應用的代碼。

Public Class Form1 
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load 
    End Sub 

    Private Sub btn1TotalCost_Click(sender As Object, e As EventArgs) Handles btn1TotalCost.Click 

     'Declaring the variables. 
     Dim MinutesAllowed As Integer 
     Dim MinutesUsed As Integer 
     Dim TextsAllowed As Integer 
     Dim TextsUsed As Integer 
     Dim DataAllowed As Integer 
     Dim DataUsed As Integer 
     Dim MinutesTotalCost As Double 
     Dim TextsTotalCost As Double 
     Dim DataTotalCost As Double 
     Dim MonthlyCost As Double 
     Dim TotalCost As Double 

     MinutesAllowed = Val(txtBoxMinutesAllowed.Text) 
     MinutesUsed = Val(txtBoxMinutesUsed.Text) 
     TextsAllowed = Val(txtBoxTextsAllowed.Text) 
     TextsUsed = Val(txtBoxTextsUsed.Text) 
     DataAllowed = Val(txtBoxDataAllowed.Text) 
     DataUsed = Val(txtBoxDataUsed.Text) 
     MinutesTotalCost = Val(txtBoxTotalCost.Text) 
     TextsTotalCost = Val(txtBoxTotalCost.Text) 
     DataTotalCost = Val(txtBoxTotalCost.Text) 
     TotalCost = Val(txtBoxTotalCost.Text) 

     'Calculation For Minutes 
     MinutesAllowed = Val(txtBoxMinutesAllowed.Text) 
     MinutesUsed = Val(txtBoxMinutesUsed.Text) 
     MonthlyCost = Val(txtBoxMonthlyCost.Text) 
     'If the minutes allowed is greater than or equal to the minutes used, no extra charge is added. 
     If MinutesAllowed >= MinutesUsed Then 
      MinutesTotalCost = 0 
     Else 'If the minutes used is greater than the minutes allowed, each minute is multiplied by 00.30p. 
      MinutesTotalCost = (MinutesUsed - MinutesAllowed) * 0.3 
     End If 
     txtBoxTotalCost.Text = CType(MinutesTotalCost + MonthlyCost, String) 



     'Calculation For Texts 
     TextsAllowed = Val(txtBoxTextsAllowed.Text) 
     TextsUsed = Val(txtBoxTextsUsed.Text) 
     MonthlyCost = Val(txtBoxMonthlyCost.Text) 
     'If the texts allowed is greater than or equal to the texts used, no extra charge is added. 
     If TextsAllowed >= TextsUsed Then 
      TextsTotalCost = 0 
     Else 'If the texts used is greater than the texts allowed, each text is multiplied by 00.15p. 
      TextsTotalCost = (TextsUsed - TextsAllowed) * 0.15 
     End If 
     txtBoxTotalCost.Text = CType(TextsTotalCost + MonthlyCost, String) 



     'Calculation For Data 
     DataAllowed = Val(txtBoxDataAllowed.Text) 
     DataUsed = Val(txtBoxDataUsed.Text) 
     MonthlyCost = Val(txtBoxMonthlyCost.Text) 
     'If the data allowed is greater than or equal to the data used, no extra charge is added. 
     If DataAllowed >= DataUsed Then 
      DataTotalCost = 0 
     Else 'If the data used is greater than the data allowed, 10.00 is added to the total cost. 
      DataTotalCost = 10 
     End If 
     txtBoxTotalCost.Text = CType(DataTotalCost + MonthlyCost + TextsTotalCost + MinutesTotalCost, Double) 
    End Sub 
End Class 

Answer 1

好的。這段代碼很殘忍，並不好。這些行

Dim FullName As String 
Dim PhoneNumber As Decimal 
Dim AccNumber As Decimal 
Dim MinutesAllowed As Integer 
Dim TextsAllowed As Integer 
Dim DataAllowed As Integer 
Dim MinutesUsed As Integer 
Dim TextsUsed As Integer 
Dim DataUsed As Integer 
Dim MonthlyCost As Double 
Dim TotalCost As Double 

正在聲明特定類型的變量 - 字符串，小數和整數等。這意味着他們只能接受相同類型的值。有選項嚴格在您的代碼中的將幫助您更正這些錯誤，因爲它會顯示您的代碼中存在的錯誤。這些行應該是：

FullName = "" 
PhoneNumber = 0D 
AccNumber = 0D 
MinutesAllowed = 0 
TextsAllowed = 0 
DataAllowed = 0 
MinutesUsed = 0 
TextsUsed = 0 
DataUsed = 0 
MonthlyCost = 0R 
TotalCost = 0R 

您遇到問題的原因是您不能將空字符串分配給整數或任何其他數字。隨着選項嚴格上，這些錯誤將顯示。 Incidendtally你會更好地聲明phoneNumber作爲一個字符串，以允許破折號和括號等。另外，如果TotalCost是一個雙倍，那麼MonthlyCost應該也是雙倍

數字後面的字母表示被分配的數字的類型。 D意味着它是一個十進制0和R意味着它是一個雙0。然而，在你的代碼中，當聲明變量時，它們已經被分配了默認值，所以你並不需要這些行上述分配值

移動上..

listBox.Items.Add("Full Name: " + txtBoxFullName.Text) 
listBox.Items.Add("Phone Number: " + txtBoxPhoneNumber.Text) 

等

的線是完全不相關的上面的變量聲明。這是故意的嗎？例如txtBoxFullName.Text與FullName不是同一個變量，除非你有其他代碼，我沒有看到需要上述變量。我猜你所發佈的代碼是不完整的。當你發佈一個問題時，你真的需要發佈所有相關的代碼。看看這裏.. https://stackoverflow.com/help/mcve

聽聽Plutonix - 他是WISE。