Create a program that allows users to enter an item code, a quantity, and a cost
per item for an order and outputs the total for the order. You need to:
• Write the declaration for the data structures you will use to store the data.
Unfortunately, your task list has left out the logical starting point, which is to design a form in a way that allows those procedures to be carried out.
The user needs to enter an item code, a quantity and a cost. So you will need a text box for each of those. These will be txtItem, txtQuantity and txtPrice. You could also have a text box to dsplay a total - txtTotal.
If the user is going to do this up to ten times you need a button for the user to say "here is the information for one item". It does what I think yo are trying to do witht he TextChanged event. This is btnCalculate. You should also
let the user know what they have done so far - I would recommend a list box - ListBox1 in this example. You also might need a button for the user to say "That's the end of the order" (although you could display a continuous update (as in this example),
so there's no need for that).
You will need a structure for each line of the order. I assume you have done structures already, although your instructions might have used that term somewhat loosely. A structure for the order line looks like this:
Private Structure OrderLine
Dim LineItem As String
Dim LineQuantity As Integer
Dim LinePrice As Decimal
Public Sub New(ByVal Item As String, ByVal Quantity As Integer, ByVal Price As Decimal)
LineItem = Item
LineQuantity = Quantity
LinePrice = Price
End Sub
Public Overloads Function ToString() As String
Return LineItem & " " & LinePrice.ToString _
& " " & LineQuantity.ToString _
& " " & (LinePrice * CDec(LineQuantity)).ToString
End Function
End Structure
Note how I have declared a constructor (the New sub) for the structure, and a ToString. These aren't strictly needed, but they are included here to show how using a structure can simplify your code.
Now you need to get the user input. This happens in the button click event for the ""here is the information for one item" button. The item code is simply a string, so it's easy. The others must be checked to ensure they are valid. The whole
thing looks like this:
Option Strict On
Public Class Form1
Dim OrderLines As List(Of OrderLine) = New List(Of OrderLine)
Private Sub btnCalculate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalculate.Click
Dim intQuantity As Integer
If Not Integer.TryParse(txtQuantity.Text, intQuantity) Then
MsgBox("Error in entering quantity")
Exit Sub
End If
Dim decPrice As Decimal
If Not Decimal.TryParse(txtPrice.Text, decPrice) Then
MsgBox("Error in entering price")
Exit Sub
End If
Dim decTotal As Decimal = decPrice * CDec(intQuantity)
txtTotal.Text = decTotal.ToString
OrderLines.Add(New OrderLine(txtItem.Text, intQuantity, decPrice))
ListUpdate()
End Sub
Private Sub ListUpdate()
ListBox1.Items.Clear()
For Each O As OrderLine In OrderLines
ListBox1.Items.Add(O.ToString)
Next
End Sub
Private Structure OrderLine
Dim LineItem As String
Dim LineQuantity As Integer
Dim LinePrice As Decimal
Public Sub New(ByVal Item As String, ByVal Quantity As Integer, ByVal Price As Decimal)
LineItem = Item
LineQuantity = Quantity
LinePrice = Price
End Sub
Public Overloads Function ToString() As String
Return LineItem & " " & LinePrice.ToString _
& " " & LineQuantity.ToString _
& " " & (LinePrice * CDec(LineQuantity)).ToString
End Function
End Structure
End Class
Note the list is used for the order lines. Note also how the ToString method of the structure is used to desplay each order line int eh list. You
must look up the TryParse method in the online help so you can see what this statement is doing and how it works.
• Write the code you will use to input the data. Assume that you are getting
the data from TextBox controls.
That's very poor expression - you do not input the data. You put code in the button click event (as above) to get the data that the user has already input. 'Input' as used here must mean "create an order line data structure, and populate it with
the data input by the user".
• Allow the user to enter up to 10 different items.
Not done in this example. You need to add code to check the size of the list to see if the user has exceeded the limit. Note that this part of the assignment might have been included because there was an assumption that you would use arrays (some of
these exercises are very old). As you are using a List instead of arrays then there is no need for such a restriction.
• Write the code for determining the order total.
The total for each line is done for the txtTotal textbox, and also in the ToString method of the structure. A useful extra-credit exercise is to create a method in the structure that returns the total for you, so you are not doing the calculation
in two different places.
To create the order total you need to iterate through your list of order lines, accumulating the line totals. That could be done in the ListUpdate method.
VB code for total price
