Help....Having trouble converting to Double from String in VB. Can anyone see the problem??

Question

Public Class frmWaiter

  Private Sub btnCalculate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalculate.Click

    'Bill Amount Input Box
    Dim txtBillAmount As String
    Dim txtBillTitle As String
    Dim txtBillPrompt As String
    Dim dblBillAmount As Double

    txtBillTitle = "Bill Amount"
    txtBillPrompt = "Enter the bill amount"
    txtBillAmount = InputBox(txtBillPrompt, txtBillTitle)
    dblBillAmount = CDbl(txtBillAmount.Text)

    'Tip Amount Input Box
    Dim txtTipAmount As String
    Dim txtTipTitle As String
    Dim txtTipPrompt As String
    Dim dblTipAmount As Double
    txtTipTitle = "Tip Amount"
    txtTipPrompt = "Enter the tip amount in percent"
    txtTipamount = InputBox(txtTipPrompt, txtTipTitle)
    dblTipAmount = CDbl(txtTipAmount)

    'Result Calculation
    Dim dblResult As Double
    Dim txtResult As String
    dblResult = dblBillAmount * dblTipAmount
    txtResult = CStr(dblResult)

    txtResult = CStr(txtResult)




  End Sub

End Class

Answer 1

a string variable does not have a .Text property, so this line should be:

dblBillAmount = CDbl(txtBillAmount)

however, I would do a couple things differently to shorten your code.

First put your variable declaration in the same line as your InputBox. And I would just put the Title and Prompt in the overloads for the InputBox instead of creating a variable.

And use Double.TryParse instead of CDbl, unless you never make a typing mistake. try typing 25w in your first inputbox and see what I mean.

then a little trick: use FormatCurrency to display the results.

try this in a test app with 1 button and 1 label

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim txtBillAmount As String = InputBox("Enter the Bill Amount", "Bill Amount")
        Dim txtTipAmount As String = InputBox("Enter the tip amount in percent", "Tip Amount")

        Dim dblBillAmount As Double
        Dim dblTipAmount As Double

        If Not Double.TryParse(txtBillAmount, dblBillAmount) OrElse Not Double.TryParse(txtTipAmount, dblTipAmount) Then
            MessageBox.Show("Invalid entry")
            Exit Sub
        End If

        dblTipAmount /= 100

        'Result Calculation
        Label1.Text = "Amount of Tip: " & FormatCurrency(dblBillAmount * dblTipAmount)

    End Sub

Answer 2

Thank you so much!  I'll try it out