'-----------------------------------------------------------------------

'    WORKING WITH SESSION STATE VARIABLES & Custom Error Pages

'                                        C# 206 Class

'                                    Created 10/16/05
'-----------------------------------------------------------------------

'This program lets users practice addition fact. The numbers they enter and the amt correct
'are stored in session variables so we can use them across round trips.

'The program tracks number of items correct, number of items given, and the percentage correct
'I use the C# random number generator to create the problems and use a range of 1-40 for the possible
'values.

'Session variables are like super global variables to the programmer because we can access them from anywhere
'in our application.

'Notes:
'EnableViewState=False for the entire doument because we are saving our data in session state variables.
'The web.config has been changed so that any error will show the default-error.htm page I created.

'Open web.config and look under Custom errors. Usually it says <customErrors mode="RemoteOnly" />
'Notice I changed it to <customErrors mode="On"   defaultRedirect="default-error.htm"/>.
'I left the original in the commented section so you can use either one by commenting out the one
'you do not want.



Public Class WebForm1
    Inherits System.Web.UI.Page


    '---I need these from several places
    Dim m_TotalItems As Integer
    Dim m_TotalRight As Integer
    Dim m_FirstNumber As Integer
    Dim m_SecondNumber As Integer
    Dim m_randomNumber As Random

    Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load



        '---first time loading we start clean. Initialize Session variables
        If Not IsPostBack Then
            Session("m_TotalItems") = 0
            Session("m_TotalRight") = 0
            Session("FirstNumber") = 0
            Session("SecondNumber") = 0

            Shuffle()    'create the numbers for the problems
        Else
            '---they are in the process of doing probs so get the stuff that was on screen on the last
            'http request. We grab data from our session variables and assign them
            m_TotalItems = Session("m_TotalItems")
            m_TotalRight = Session("m_TotalRight")
            m_FirstNumber = Session("FirstNumber")
            m_SecondNumber = Session("SecondNumber")
        End If
        RefreshDisplay()       'now show numbers 

    End Sub

    Private Sub Shuffle()

        Dim Min As Integer = 1
        Dim Max As Integer = 40


        '---get random numbers in the range of 1-40
        m_randomNumber = New Random

        m_FirstNumber = m_randomNumber.Next(Min, Max)
        m_SecondNumber = m_randomNumber.Next(Min, Max)

        '---now save these numbers
        Session("FirstNumber") = m_FirstNumber
        Session("SecondNumber") = m_SecondNumber

    End Sub
    Private Function Answer() As Integer
        '---calculate answer
        Answer = m_FirstNumber + m_SecondNumber

    End Function

    Private Sub RefreshDisplay()

        lblFirst.Text = m_FirstNumber
        lblSecond.Text = "+ " & m_SecondNumber

    End Sub
    Private Sub txtAnswer_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtAnswer.TextChanged

        '---we showed them another prob so increment, save, & display it
        m_TotalItems += 1
        Session("m_TotalItems") = m_TotalItems
        lblNumItems.Text = m_TotalItems

        If txtAnswer.Text = Answer() Then
            lblComment.Text = "Correct!"

            '---now let's keep track of how many they get right
            '---increment number of items & correct answers
            Session("m_TotalRight") += 1
            m_TotalRight += 1

            '---show another prob
            txtAnswer.Text = ""
            Shuffle()
            RefreshDisplay()

        Else
            txtAnswer.Text = ""
            lblComment.Text = "Sorry, try again."
        End If

        '---now show how many they got right. Use the Session because they may have not gotten
        'it right and we have to use the latest value.
        lblCorrect.Text = CStr(Session("m_TotalRight"))

        '---show percent correct
        If m_TotalRight > 0 Then
            lblPercent.Text = CInt(m_TotalRight / m_TotalItems * 100)
        End If

    End Sub
End Class