Need explanation

[hd82]

First i would like to say hi i am new here and new to programming. im currently takeing an intor to progrmming class useing vb 2008 express edition. so basicly im a newbe. now as for my question. i had to write a program for class as a lab assignment The 12 days of christmas. i was able to write part of it but couldnt quite get it runnin rite. finaly my teacher sat down real fast and fixed my mistakes so it runs fine and i handed it in. the problem im havein is that the professor didnr explain to me wat i did wrong or why wat she did works so i have no idea whats what in the program. it basicly comes down to i dont understand Loops, For Next, or Arrays. if someone could explain to me wats goin on in the program and why it all works i think it would help me understand things finally. heres the code, runs perfectly and does exactly wat it is supposed to.

Public Class frm12DaysOfChristmas
    Dim itemName(12) As String
    Dim itemCost(12) As Double
 
 
    Private Sub btnDisplay_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDisplay.Click
        Dim InputDay As Integer
        Dim CostOfDay As Double = 0
        Dim TotalCost As Double = 0
        InputDay = CInt(mtxtDayNumber.Text)
        lstResults.Items.Clear()
        If (CInt(InputDay) <= 0) Or (CInt(InputDay) >= 13) Then
            MsgBox("Please enter a number from 1 to 12")
            mtxtDayNumber.Clear()
            mtxtDayNumber.Focus()
        Else
            For dayNum As Integer = 1 To InputDay
                lstResults.Items.Add(itemName(dayNum))
                CostOfDay = dayNum * itemCost(dayNum) + CostOfDay
            Next
            lstResults.Items.Add(FormatCurrency(CostOfDay))
            CostOfDay = 0
            'Grand Total
            For iCount As Integer = 1 To 12
                For dayNum As Integer = 1 To iCount
                    CostOfDay = dayNum * itemCost(dayNum) + CostOfDay
                Next
            Next
            lstResults.Items.Add("Total Cost " & (FormatCurrency(CostOfDay)))
        End If
    End Sub
    Private Sub frm12DaysOfChristmas_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        itemName(1) = "1 Partridge in a pear tree"
        itemName(2) = "2 Turtle doves"
        itemName(3) = "3 French hens"
        itemName(4) = "4 Calling birds"
        itemName(5) = "5 Golden rings"
        itemName(6) = "6 Geese a laying"
        itemName(7) = "7 Swans a swimming"
        itemName(8) = "8 Maids a milking"
        itemName(9) = "9 Ladies dancing"
        itemName(10) = "10 Lords a leaping"
        itemName(11) = "11 Pipers piping"
        itemName(12) = "12 Drummers drumming"
 
        itemCost(1) = 164.99
        itemCost(2) = (20.0)
        itemCost(3) = (15.0)
        itemCost(4) = (149.99)
        itemCost(5) = (79.0)
        itemCost(6) = (60.0)
        itemCost(7) = (600.0)
        itemCost(8) = (5.85)
        itemCost(9) = (528.8)
        itemCost(10) = (428.51)
        itemCost(11) = (201.22)
        itemCost(12) = (199.82)
    End Sub
End Class

[hd82]

anyone out their to offer help

[PRR]

Can you explain what your program does? Then maybe it will be easier to say something. Its difficult to read code and "get" the whole picture.

[Frinavale]

I seriously dislike VB.NET for loops.
C# loops are so much nicer (the same loop syntax for C++, Java, JavaScript and other languages too)

Let's ignore your program for the time being and take a look at the following loop:

For counter As Integer = 1 to 10
  'do stuff
Next

This loop declares a variable "counter" as an Integer and sets it to 1.
It's a short hand version of:

Dim counter As Integer = 1
For counter To 12
  'do stuff
Next
 

The for loop will loop from 1 to 12 in this case and then end.
You can access what loop iteration you're at using the "counter" variable.
Say you had the following array of Strings:

Dim myArrayOfTwelveNumbers(12) As String= {"zero","one","two","three","four","five","six","seven","eight","nine","ten","eleven","twelve"}
'The above array has been declared to hold 13 strings that contain text for numbers 0 - 12
 

You can loop through this array and print each the text stored in each element by accessing the element at "counter" for each loop iteration:

Dim myArrayOfTwelveNumbers(12) As String= {"zero","one","two","three","four","five","six","seven","eight","nine","ten","eleven","twelve"}
For counter As Integer = 1 To 12
  Console.WriteLine(myArrayOfTwelveNumbers(counter))
Next
 

This will print:

one
two
three
four
five
six
seven
eight
nine
ten
eleven
twelve

Note that "zero" is not printed. That is because "zero" exists at the array index 0 and you are looping from 1 to 12.

If you only wanted to print "four","five","six" you'd start the loop at element 4 instead:

Dim myArrayOfTwelveNumbers(12) As String= {"zero","one","two","three","four","five","six","seven","eight","nine","ten","eleven","twelve"}
For counter As Integer = 4 To 6
  Console.WriteLine(myArrayOfTwelveNumbers(counter))
Next
 

It's pretty simple....but I still hate them.

-Frinny

[hd82]

to prr, the prgram is supposed to request an integer from 1 through 12 and then list the gifts for that day along with that days cost. on the nth day, the n gifts are 1 partridge in a pear tree, 2 turtle doves,... n of the nth item. the prgram should also give the total cost of all twelve days.

[PRR]

I guess Frinavale has answered pretty much most of your queries. Adding to her ans, you can look into:
Convert to int
Switch statement