Calculate fees for membership

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I'm creating a library system so far i've come to a step where i need to calculate and late fees occured by members. How can i achieve this.
The fee they pay is based on the number of days late. for e.g no days late = 3
charege should = £2
total fee = £2

Please can someone try to help me achieve this task.

here is my code:

VB

Dim latecharge, total As Decimal
Dim days As Integer

If txtdays.Text < 0 Then
    MsgBox("error !", MsgBoxStyle.Critical)
Else

End If

Select Case days
    Case 1 To 5
        txtlate.Text = 2
    Case 6 To 10
        txtlate.Text = 5
    Case 11 To 15
        txtlate.Text = 7.5
    Case 16 To 20
        txtlate.Text = 10
    Case Is > 20
        MsgBox("Remove member")
End Select

latecharge = days
txtlate.Text = latecharge

but it dont seem to be working can someone kindly point out whats wrong.

Posted 12-Feb-12 5:05am

alom_93

Updated 12-Feb-12 5:32am

Sander Rossel

v2

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Sander Rossel · Answer 1 · 2012-02-12T05:53:00

Basically your code makes no sense...
txtDays is, I presume, a regular TextBox[^] that is probably not validated. But let's assume, for this example, txtDays can only hold numeric values.
If the number of days entered is negative you show a MessageBox[^], may I suggest using the MessageBox.Show Method[^] (.NET) instead of MsgBox[^] (VB).
The next part of your code is a Select Case Statement[^] which checks for the value of the days variable. However, days is never set and thus will always be 0.
So now, let's say days IS set somewhere, you then show the amount of pounds this person has to pay. Well, I would certainly wait with returning my books, because after 20 days I only get a MessageBox and appearently don't have to pay for anything :)
The next part of your code is just the weirdest... You're saying latecharge is equal to days (which still isn't set) and then txtLate.Text is equal to latecharge... You might as well set txtLate.Text to days immediately. However, since you are using this TextBox to show the fee this person has to pay you are overwriting that value... Besides, the user already knows the days because he or she entered this himself! Also, your total variable does nothing and is just sitting there.
Now consider this:

VB

Dim daysLate As Integer
' Check if the entered value is numeric.
If Not Integer.TryParse(txtDays.Text, daysLate) Then
    MessageBox.Show("Please enter a numeric value.", Me.Text, MessageBoxButtons.OK, MessageBoxIcon.Error)
Else
    If daysLate < 0 Then
        MessageBox.Show("Please enter a value higher than 0.", Me.Text, MessageBoxButtons.OK, MessageBoxIcon.Error)
    Else
        Select Case days
            Case 1 To 5
                txtLate.Text = "2"
            Case 6 To 10
                txtLate.Text = "5"
            Case 11 To 15
                txtLate.Text = "7.5"
            Case 16 To 20
                txtLate.Text = "10"
            Case Is > 20
                MessageBox.Show("This member has exceeded the maximum number of days late.", Me.Text, MessageBoxButtons.OK, MessageBoxIcon.Information)
        End Select
    End If
End If

Now this would work, however... If the library is going to use different fees or days you will have to rewrite your software and re-deploy! So I suggest you store the days and fees in a database somewhere and recover them here...
However, since you seem to be quite lost as to what to do and how to do it I suggest you start reading some books first. There is plenty of reference material, both on the internet and in the library you are writing this software for.
By the way, is this homework? If it is I suggest you study a bit harder :)