为什么我不能返回正确的变量？

Question

我无法在应用程序中为小计返回正确的值。用户选择他们想要的旅游类型，并输入要购买的票数。按“计算成本”按钮后，将显示小计，税额和最终总计。

我的小计方法代码和btnCost_Click如下：

Private Sub btnCost_Click(sender As Object, e As EventArgs) Handles btnCost.Click
    Dim intTicketQuantity As Integer
    Dim blnNumberOfTicketsIsValid As Boolean = False
    Dim blnCheckForRad As Boolean = False
    Dim decSubTotal As Decimal
    Dim decTotalTax As Decimal
    Dim intTourType As Integer

    blnNumberOfTicketsIsValid = ValidateNumberOfTickets()

    If (blnNumberOfTicketsIsValid) Then
        intTicketQuantity = Convert.ToInt32(txtTickets.Text)
        intTicketQuantity = cboTourType.SelectedIndex
        If (intTicketQuantity > 0) Then
            intTourType = cboTourType.SelectedIndex
        End If

        Select Case intTourType
            Case 0
                decSubTotal = Story(intTourType, intTicketQuantity)
                decTotalTax = Tax(decSubTotal)
            Case 1
                decSubTotal = Battleground(intTourType, intTicketQuantity)
                decTotalTax = Tax(decSubTotal)
            Case 2
                decSubTotal = Mission(intTourType, intTicketQuantity)
                decTotalTax = Tax(decSubTotal)
        End Select
        ShowAll(decSubTotal, decTotalTax)
    End If
End Sub

Private Function Story(ByVal intTourType As Integer, intTicketQuantity As Integer) As Decimal
    Dim decSubTotal As Decimal = 0D

    If (radWeekday.Checked = True) Then
        decSubTotal = 19D * intTicketQuantity * (1 - _decDiscount)
    ElseIf (radWeekend.Checked = True) Then
        decSubTotal = 19D * intTicketQuantity
    End If
    Return decSubTotal
End Function

Private Function Battleground(ByVal intTourType As Integer, intTicketQuantity As Integer) As Decimal
    Dim decSubTotal As Decimal = 0D

    If (radWeekday.Checked = True) Then
        decSubTotal = 29D * intTicketQuantity * (1 - _decDiscount)
    ElseIf (radWeekend.Checked = True) Then
        decSubTotal = 29D * intTicketQuantity
    End If
    Return decSubTotal
End Function

Private Function Mission(ByVal intTourType As Integer, intTicketQuantity As Integer) As Decimal
    Dim decSubTotal As Decimal = 0D

    If (radWeekday.Checked = True) Then
        decSubTotal = 49D * intTicketQuantity * (1 - _decDiscount)
    ElseIf (radWeekend.Checked = True) Then
        decSubTotal = 49D * intTicketQuantity
    End If
    Return decSubTotal
End Function