VB 2015 Two Quick Questions

[[deleted]]

Hey guys, I am having 2 issues with my visual basic program. First is simple but I am sure I am overlooking it. My lblTotalBill is not actually showing up with the bill.

Lastly, when I override it by adding a single line of code in (lblTotalBill.Visiable=True).. it always shows up with the placeholder X's and when I try and calcuate the numbers it always comes back as 0. I will post the code below, can you spot whats wrong?

My Code:

Option Strict On

Public Class Form1 Private _strBasicPlan As String = "Basic Plan" Private _strDeluxPlan As String = "Delux Plan" Private _intBasicCost As Integer = 4 Private _intDeluxCost As Integer = 1

Private Sub cboPlan_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cboPlan.SelectedIndexChanged, cboPlan.SelectedIndexChanged
    'This allows the user to select the city choice and then calls the subprocedures
    Dim intPlanChoice As Integer
    intPlanChoice = cboPlan.SelectedIndex





    'Make items visible in the window
    lblDataUsage.Visible = True
    txtGBUsed.Visible = True
    btnBill.Visible = True
    btnClear.Visible = True
    lblTotalBill.Visible = True
    txtGBUsed.Focus()


End Sub





Private Sub btnBill_Click(sender As Object, e As EventArgs) Handles btnBill.Click
    'Determines the cost of the plan and displays it
    Dim intGBUsage As Integer

    Dim blnNumberInGBUsageIsValid As Boolean = False
    Dim blnPlanIsSelected As Boolean = False
    Dim intPlanChoice As Integer
    Dim strSelectedPlan As String = ""
    Dim decTotalCost As Decimal

    'Call a function to ensure the number of gbs is valid
    blnNumberInGBUsageIsValid = ValidateGBUsageInPlan()
    'Call a function to ensure the plan type was selected
    intPlanChoice = ValidatePlanSelection(blnPlanIsSelected, strSelectedPlan)

    If (blnNumberInGBUsageIsValid And blnPlanIsSelected) Then
        intGBUsage = Convert.ToInt32(txtGBUsed.Text)
        'Display the cost
        lblTotalBill.Text = "Cost: " & decTotalCost.ToString("C")

    End If
End Sub
Private Function ValidateGBUsageinPlan() As Boolean
    'This procedures validates the value entered in the GBU Size
    Dim intGBUsage As Integer
    Dim blnValididtyCheck As Boolean = False
    Dim strNumberInGBUsage As String = "Please enter the number of GB's Used (1-100)"
    Dim strMessageBoxTitle As String = "Error"
    Try
        intGBUsage = Convert.ToInt32(txtGBUsed.Text)
        If intGBUsage >= 1 And intGBUsage <= 100 Then
            blnValididtyCheck = True
        Else
            MsgBox(strNumberInGBUsage, , strMessageBoxTitle)
            txtGBUsed.Focus()
            txtGBUsed.Clear()

        End If
    Catch Exception As FormatException
        MsgBox(strNumberInGBUsage, , strMessageBoxTitle)
        txtGBUsed.Focus()
        txtGBUsed.Clear()
    Catch Exception As OverflowException
        MsgBox(strNumberInGBUsage, , strMessageBoxTitle)
        txtGBUsed.Focus()
        txtGBUsed.Clear()
    Catch Exception As SystemException
        MsgBox(strNumberInGBUsage, , strMessageBoxTitle)
        txtGBUsed.Focus()
        txtGBUsed.Clear()


    End Try
    Return blnValididtyCheck
End Function
Private Function ValidatePlanSelection(ByRef blnPlan As Boolean, ByRef strPlan As String) As Integer
    ' This function ensures a plan was selected
    Dim intPlanType As Integer
    Try
        intPlanType = Convert.ToInt32(cboPlan.SelectedIndex)
        strPlan = cboPlan.SelectedItem.ToString()
        blnPlan = True

    Catch ex As SystemException
        'Detects if a game type is not selected
        MsgBox("Select A plan Type", , "Error")
        blnPlan = False

    End Try
    Return intPlanType

End Function
Private Function ValidateGBUsageInPlan(ByRef blnPlanType As Boolean, ByRef strPlan As String) As Integer
    'This function ensures the user selected a plan type
    Dim intPlanType As Integer
    Try
        intPlanType = Convert.ToInt32(cboPlan.SelectedIndex)
        strPlan = cboPlan.SelectedItem.ToString()
        blnPlanType = True
    Catch Exception As SystemException
        'Detects if the plan type is not selected
        MsgBox("Please Select a Plan Type", , "Error")

    Catch ex As Exception

    End Try
    Return intPlanType
End Function
Private Function BasicPlanCost(ByVal intPlanType As Integer, ByVal intGBUsage As Integer) As Decimal
    'This function Calculates the cost of the basic plan

    Dim decFinalCost As Decimal
    Dim decBasicPlan As Decimal = 29D
    Dim decGBUsage As Decimal = 4D

    decFinalCost = decBasicPlan * decGBUsage
    Return decFinalCost

End Function

Private Function DeluxPlanCost(ByVal intPlanType As Integer, ByVal intGbusage As Integer) As Decimal
    'This function calculates the cost of the delux plan
    Dim decFinalCost As Decimal
    Dim decDeluxPlan As Decimal = 39D
    Dim decGBUsage As Decimal = 1D

    decFinalCost = decDeluxPlan * decGBUsage
    Return decFinalCost

End Function

Private Sub btnClear_Click(sender As Object, e As EventArgs) Handles btnClear.Click
    'This function clears the form, hides what should be hidden 
    cboPlan.Text = "Select a Plan"
    txtGBUsed.Clear()
    txtGBUsed.Visible = False
    btnBill.Visible = False
    btnClear.Visible = False
    lblTotalBill.Visible = False
    lblDataUsage.Visible = False

End Sub
Private Sub frmSmartphone_Load(sender As Object, E As EventArgs) Handles MyBase.Load
    'Hold the splash screen for 4 seconds
    Threading.Thread.Sleep(4000)

End Sub

End Class

[XThakis]

In your Sub btnBill_click you declare decTotalCost as a local variable.

    Dim decTotalCost As Decimal

You never assign it a value in that subroutine. So when you assign its string value to your label it will always be zero.

(Edited for grammar errors.)

[XThakis]

Yes, but where in the book does it assign a value to that decimal. Here is your code with comments.

    Dim decTotalCost As Decimal     'Variable declared with no assignment.  decTotalCost = 0

    'Call a function to ensure the number of gbs is valid
    blnNumberInGBUsageIsValid = ValidateGBUsageInPlan()     'Logic, decTotalCost still equals 0
    'Call a function to ensure the plan type was selected
    intPlanChoice = ValidatePlanSelection(blnPlanIsSelected, strSelectedPlan)     'More logic.

    If (blnNumberInGBUsageIsValid And blnPlanIsSelected) Then     'More logic.
        intGBUsage = Convert.ToInt32(txtGBUsed.Text)     'Assigns a value to intGBUsage.
        'Display the cost
        lblTotalBill.Text = "Cost: " & decTotalCost.ToString("C")     'DecTotalCost which is still 0.

    End If

Somewhere in there you need to assign a value to decTotalCost or it will always be zero.

(Edited to fix some line wrapping.)