如何添加驗證？

Question

我需要在VB中爲此代碼添加驗證。另外，如果新餘額爲負數，則顯示一個消息框。如果沒有足夠的資金支付支票，請不要扣除支票金額。相反，顯示消息「消費不足」的消息框並扣除10美元的服務費用。

我不知道如何做到這一點。

這裏是到目前爲止的代碼：

Public Class CheckingForm 
Private BalanceDecimal As Decimal 

Private Sub CalculateTextBox_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CalculateTextBox.Click 
    'Calculate the transaction and display the new balance 
    Dim AmountDecimal As Decimal 

    If DepositRadioButton.Checked Or CheckRadioButton.Checked Or ChargeRadioButton.Checked Then 
     Try 
      AmountDecimal = Decimal.Parse(AmountTextBox.Text) 

      If DepositRadioButton.Checked = True Then 
       BalanceDecimal += AmountDecimal 
      ElseIf CheckRadioButton.Checked = True Then 
       BalanceDecimal -= AmountDecimal 
      ElseIf ChargeRadioButton.Checked = True Then 
       BalanceDecimal -= AmountDecimal 
      End If 

      BalanceTextBox.Text = BalanceDecimal.ToString("C") 
     Catch AmountException As FormatException 
      MessageBox.Show("Please make sure that only numeric data has been entered.", 
       "Invalid Entry", MessageBoxButtons.OK, MessageBoxIcon.Exclamation) 
      With AmountTextBox 
       .Focus() 
       .SelectAll() 
      End With 
     Catch AnyException As Exception 
      MessageBox.Show("Error: " & AnyException.Message) 
     End Try 
    Else 
     MessageBox.Show("Please select deposit, check, or service charge", "Input needed") 
    End If 
End Sub 

Private Sub ClearTextBox_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ClearTextBox.Click 
    'Clear the form 

    DepositRadioButton.Checked = False 
    ChargeRadioButton.Checked = False 
    CheckRadioButton.Checked = False 
    With AmountTextBox 
     .Clear() 
     .Focus() 
    End With 
End Sub 

Private Sub ExitButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ExitButton.Click 
    'End the program 

    Me.Close() 
End Sub 

Private Sub PrintButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles PrintButton.Click 
    'Print the form 

    PrintForm1.PrintAction = Printing.PrintAction.PrintToPreview 
    PrintForm1.Print() 
End Sub 

Private Sub CheckingForm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load 

End Sub 
End Class 

任何幫助，將不勝感激！

Answer 1

我不確定你的問題在哪裏，但我希望這會滿足你的要求。

這條線是從你的代碼中刪除冗餘，所以你不必寫驗證兩次：

ElseIf CheckRadioButton.Checked = True OR ChargeRadioButton.Checked = True Then 

接下來的部分是檢查他是否有資格從他的賬戶或收回這筆款項不，如果不是，則阻止他並退出該函數，以使GUI或DB不受影響！

IF (BalanceDecimal - AmountDecimal > 0) THEN 
    BalanceDecimal -= AmountDecimal 
ELSE 
    'SHOW YOUR MESSAGE HERE 
    EXIT 

這是basiclly你在問問題，但是翻譯成代碼，沒有什麼棘手的只是簡單的邏輯:)）

Private Sub CalculateTextBox_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CalculateTextBox.Click 
     'Calculate the transaction and display the new balance 
     Dim AmountDecimal As Decimal 

     If DepositRadioButton.Checked Or CheckRadioButton.Checked Or ChargeRadioButton.Checked Then 
      Try 
       AmountDecimal = Decimal.Parse(AmountTextBox.Text) 

       If DepositRadioButton.Checked = True Then 
        BalanceDecimal += AmountDecimal 
       ElseIf CheckRadioButton.Checked = True OR ChargeRadioButton.Checked = True Then 
        IF (BalanceDecimal - AmountDecimal > 0) THEN 
         BalanceDecimal -= AmountDecimal 
        ELSE 
         'SHOW YOUR MESSAGE HERE 
         EXIT 
        END IF 
       END IF 

       BalanceTextBox.Text = BalanceDecimal.ToString("C") 
      Catch AmountException As FormatException 
       MessageBox.Show("Please make sure that only numeric data has been entered.", 
        "Invalid Entry", MessageBoxButtons.OK, MessageBoxIcon.Exclamation) 
       With AmountTextBox 
        .Focus() 
        .SelectAll() 
       End With 
      Catch AnyException As Exception 
       MessageBox.Show("Error: " & AnyException.Message) 
      End Try 
     Else 
      MessageBox.Show("Please select deposit, check, or service charge", "Input needed") 
     End If 
    End Sub