Trouble with conversion of "" in an equation

[Michael MacDonald]

I have written a simple program that calculates a running $ total. This
program uses a checkbox to acknowledge that that version of the ticket
is desired and it checks the Qty box to see how many tickets are
desired. Based upon the checkbox being checked and the number of tickets
desired directly affects the running grand total (of course!). OK I
have set where if ticketsDesiredT otal>0 then checkbox.checke d = true.
The only problem I have is that if the user deletes the number of
tickets and the user does not enter a number and “ ” is in the tickets
desired box the program crashes. It crashes because it is taking the
value of TicketsDesiredT otal and multiplying it by the per ticket cost.
And the debugger says it can’t convert “” to use it in the equation.
How can I make this thing work??? Here is the code and the function it
calls:

Function processor()

Dim decTtl As Decimal = 0.0

Dim strOil As String = txtQtyOil.Text
If cbOil.Checked = True Then
lblOilTtl.Text = (txtQtyOil.Text * 150.0)
decTtl += lblOilTtl.Text
End If
If cbAllies.Checke d = True Then
lblAlliesTtl.Te xt = (txtQtyAllies.T ext * 50.0)
decTtl += lblAlliesTtl.Te xt
End If
If cbWardaddy.Chec ked = True Then
lblWarTtl.Text = 0.0
decTtl += lblWarTtl.Text
End If
lblSubTotal.Tex t = String.Format(" {0:C}", decTtl)

Dim decTxTtl = CDec(decTtl * 0.07)

lblTaxTtl.Text = String.Format(" {0:C}", decTxTtl)
lblGrandTtl.Tex t = String.Format(" {0:C}", (decTxTtl + decTtl))
End Function


Private Sub cbOil_CheckedCh anged(ByVal sender As System.Object, ByVal
e As System.EventArg s) Handles cbOil.CheckedCh anged
processor()
End Sub

Private Sub cbAllies_Checke dChanged(ByVal sender As System.Object,
ByVal e As System.EventArg s) Handles cbAllies.Checke dChanged
processor()

End Sub

Private Sub cbWardaddy_Chec kedChanged(ByVa l sender As System.Object,
ByVal e As System.EventArg s) Handles cbWardaddy.Chec kedChanged
processor()

End Sub
Mike_Mac

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[Earl]

I think you gave us the wrong code or not enough of it. Nonetheless, there
are many different ways of handling an empty string that represents zero.
Two simple methods: either exit the sub when you have an empty string or
convert all empty strings to zero before doing the math. There are endless
permutations of textbox validation of course, including creating an extended
textbox class that has all the validation built-in.

"Michael MacDonald" <ma***********@ yahoo.com> wrote in message
news:%2******** ********@tk2msf tngp13.phx.gbl. ..

I have written a simple program that calculates a running $ total. This
program uses a checkbox to acknowledge that that version of the ticket
is desired and it checks the Qty box to see how many tickets are
desired. Based upon the checkbox being checked and the number of tickets
desired directly affects the running grand total (of course!). OK I
have set where if ticketsDesiredT otal>0 then checkbox.checke d = true.
The only problem I have is that if the user deletes the number of
tickets and the user does not enter a number and " " is in the tickets
desired box the program crashes. It crashes because it is taking the
value of TicketsDesiredT otal and multiplying it by the per ticket cost.
And the debugger says it can't convert "" to use it in the equation.
How can I make this thing work??? Here is the code and the function it
calls:

Function processor()

Dim decTtl As Decimal = 0.0

Dim strOil As String = txtQtyOil.Text
If cbOil.Checked = True Then
lblOilTtl.Text = (txtQtyOil.Text * 150.0)
decTtl += lblOilTtl.Text
End If
If cbAllies.Checke d = True Then
lblAlliesTtl.Te xt = (txtQtyAllies.T ext * 50.0)
decTtl += lblAlliesTtl.Te xt
End If
If cbWardaddy.Chec ked = True Then
lblWarTtl.Text = 0.0
decTtl += lblWarTtl.Text
End If
lblSubTotal.Tex t = String.Format(" {0:C}", decTtl)

Dim decTxTtl = CDec(decTtl * 0.07)

lblTaxTtl.Text = String.Format(" {0:C}", decTxTtl)
lblGrandTtl.Tex t = String.Format(" {0:C}", (decTxTtl + decTtl))
End Function


Private Sub cbOil_CheckedCh anged(ByVal sender As System.Object, ByVal
e As System.EventArg s) Handles cbOil.CheckedCh anged
processor()
End Sub

Private Sub cbAllies_Checke dChanged(ByVal sender As System.Object,
ByVal e As System.EventArg s) Handles cbAllies.Checke dChanged
processor()

End Sub

Private Sub cbWardaddy_Chec kedChanged(ByVa l sender As System.Object,
ByVal e As System.EventArg s) Handles cbWardaddy.Chec kedChanged
processor()

End Sub
Mike_Mac

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[Cor Ligthert]

Hi Michael,

Probabley the most simple thing is to set in top of your program
Option Strict On,

Than you are told that you cannot do a
myString = 1 * 3
There are a lot of simple conversions in Visual Basic which are very handy
and extends very much the single dotNet namespace. By instance Cint (convert
to integer) and Cdbl (convert to double).

If you have more questions about this please reply, not any problem at all.
However place first that Option Strict On

I hope this helps?

Cor

I have written a simple program that calculates a running $ total. This
program uses a checkbox to acknowledge that that version of the ticket
is desired and it checks the Qty box to see how many tickets are
desired. Based upon the checkbox being checked and the number of tickets
desired directly affects the running grand total (of course!). OK I
have set where if ticketsDesiredT otal>0 then checkbox.checke d = true.
The only problem I have is that if the user deletes the number of
tickets and the user does not enter a number and " " is in the tickets
desired box the program crashes. It crashes because it is taking the
value of TicketsDesiredT otal and multiplying it by the per ticket cost.
And the debugger says it can't convert "" to use it in the equation.
How can I make this thing work??? Here is the code and the function it
calls:

Function processor()

Dim decTtl As Decimal = 0.0

Dim strOil As String = txtQtyOil.Text
If cbOil.Checked = True Then
lblOilTtl.Text = (txtQtyOil.Text * 150.0)
decTtl += lblOilTtl.Text
End If
If cbAllies.Checke d = True Then
lblAlliesTtl.Te xt = (txtQtyAllies.T ext * 50.0)
decTtl += lblAlliesTtl.Te xt
End If
If cbWardaddy.Chec ked = True Then
lblWarTtl.Text = 0.0
decTtl += lblWarTtl.Text
End If
lblSubTotal.Tex t = String.Format(" {0:C}", decTtl)

Dim decTxTtl = CDec(decTtl * 0.07)

lblTaxTtl.Text = String.Format(" {0:C}", decTxTtl)
lblGrandTtl.Tex t = String.Format(" {0:C}", (decTxTtl + decTtl))
End Function


Private Sub cbOil_CheckedCh anged(ByVal sender As System.Object, ByVal
e As System.EventArg s) Handles cbOil.CheckedCh anged
processor()
End Sub

Private Sub cbAllies_Checke dChanged(ByVal sender As System.Object,
ByVal e As System.EventArg s) Handles cbAllies.Checke dChanged
processor()

End Sub

Private Sub cbWardaddy_Chec kedChanged(ByVa l sender As System.Object,
ByVal e As System.EventArg s) Handles cbWardaddy.Chec kedChanged
processor()

End Sub
Mike_Mac

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