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Question

I have an assignment that we have an existing GUI and all I have to do is code is in VB.Net to function like a cash register. seems easy enough right? but remember I'm just learning...so I have a textbox the user inputs a price, a label to have a running subtotal, a label for the tax amount, and a label for the grand total. Also the gui has an enter button which is clicked after each price and will add to the subtotal, then there is a total button that when clicked figures the tax amount and displays it as well as the grand total is figures and displayed.

so here is what I have for the enter button (just to add the prices for a subtotal) but every time I click a new price- and then enter the new price isn't added to the subtotal- instead the subtotal is whatever price I just typed in... so here is my code. Can someone tell me what I am missing or have done wrong?

Dim currentPrice As Decimal
Dim subtotal As Decimal

currentPrice = Val(currentPriceTextBox.Text)
'add the items values
      total = subtotal + currentPrice

      'display subtotal
      subtotalValueLabel.Text = String.Format("{0:C}", total)

      'clear item price box
      currentPriceTextBox.Text = ""

      If currentPrice > 0 Then
         total = Val(subtotalValueLabel.Text) + currentPrice
      End If



   End Sub

Bohdan · Accepted Answer

The advise to do subtotal = subtotalValueLabel.text whould be correct one but not in your case. Because you format the lable text to show a dollar sign before the price, it would requeir more code to convert it back to a number. That is why subtotal always becomes zero. 

The easiest way in your case is to declare subtotal as a global variable. Meaning it should be decared outside of your Sub procedure. The code will look something like this:

    Dim subtotal As Decimal

'this is the procedure for click event
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim currentPrice As Decimal

        currentPrice = Val(currentPriceTextBox.Text)

        'add the items values
        subtotal = subtotal + currentPrice

        'display subtotal
        subtotalValueLabel.Text = String.Format("{0:C}", subtotal)

        'clear item price box
        currentPriceTextBox.Text = ""

    End Sub

you would have to do similar thing to calculate grand total

Abraham Alex · Answer

Its because you have not initialised the variable subtotal 

You have declared subtotal 
Dim subtotal As Decimal

And then straight away used it in the equation
total = subtotal + currentPrice

At this stage, since subtotal does not have any value and hence is euqial to zero.

hence total = 0 + currentPrice which is equal to currentPrice

trascopur · Answer

The problem is that when you declare "Dim subtotal As Decimal", you are essentially setting "subtotal" to zero. You need to save the existing value of subtotalValueLabel as subtotal before doing the "total = subtotal + currentPrice." Add something like "subtotal = subtotalValueLabel.text" after "Dim subtotal As Decimal."

mayze · Answer

i ought to apply a for loop, and for simplicity count number the printing one after the different. int count number =2; //Initialize one counter (for the output) for(int i=a million;i<=10;i++){ //for loop, starts at one repeats 10 circumstances device.out.println(count number); //print the counter count number=count number+2; //increment counter } via ways i++ is a similar as putting forward i=i+a million

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Newbie programming student needs help...?

4 Answers