VB.Net: Grade Calculator Program - Getting Ridiculous Values - vb.net

Question

I am attempting to create a grade calculator program and I am having some two problems:
Getting the right outputs (because I am getting ridiculous numbers) and
Getting my counters to work.
The basic form is basically one enters 7 input grades:
3 exams (weighed 15%, 20%, and 20% respectively)
A project (weighed 10%),
Assignments (weighed 20%),
Peer reviews (weighed 5%) ,
A programming language presentation (weighed 10%)
and the individual is supposed to get an output of their numeric grade, their letter grade, and two counters that count how many people got A's and F's.
For an example when I enter 3 exam grades: 82,87,91; Assignments: 94; Peer reviews: 100; programming language presentation: 90; and final project: 92,
I get a final numeric grade of 253.90 and a letter grade of F when it clearly should be a letter grade of A and numeric 89.90.
My counters also are not working properly because they aren't displaying the count, but I feel like I put it in the right place (displaying outputs). What exactly am I doing wrong here? Here's my code
Option Strict On
Public Class frmGradeCalculator
'declare Constants
Const EXAM1GRADE_WEIGHT As Decimal = 0.15D
Const EXAM2GRADE_WEIGHT As Decimal = 0.2D
Const EXAM3GRADE_WEIGHT As Decimal = 0.2D
Const HOMEWORKGRADE_WEIGHT As Decimal = 0.2D
Const HOMEWORKPEERREVIEW_WEIGHT As Decimal = 0.05D
Const LANGUAGEQUICKREFERENCE_WEIGHT As Decimal = 0.1D
Const FINALPROJECT_WEIGHT As Decimal = 0.1D
'Declare module variables
Dim mdecFinalNumericGrade As Decimal
Dim mstrFinalLetterGrade As String
Dim mintStudentsWithAs As Integer
Dim mintStudentsWithFs As Integer
Private Sub btnCalculate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalculate.Click
'declare variables
Dim decExam1Grade As Decimal
Dim decExam2Grade As Decimal
Dim decExam3Grade As Decimal
Dim decHomeworkGrade As Decimal
Dim decPeerReviewGrade As Decimal
Dim decLanguageReferenceGrade As Decimal
Dim decFinalProjectGrade As Decimal
Dim decPercent As Decimal
'check for blanks
If (txtExam1Grade.Text) = "" Then
MessageBox.Show("You Can't Leave Exam 1 Blank")
Exit Sub
End If
'check for numeric
If IsNumeric(txtExam1Grade.Text) = False Then 'value is not numeric
MessageBox.Show("Please enter a numeric value for Exam 1!")
Exit Sub
End If
'check for blanks
If (txtExam2Grade.Text) = "" Then
MessageBox.Show("Please enter Exam 2!")
Exit Sub
End If
'check for everything else
If IsNumeric(txtExam2Grade.Text) = False Then 'Value is not numeric
MessageBox.Show("Please enter a numeric value for Exam 2!")
Exit Sub
End If
'check for blanks
If (txtExam3Grade.Text) = "" Then
MessageBox.Show("Please enter Exam 3!")
Exit Sub
End If
'check for numerics
If IsNumeric(txtExam3Grade.Text) = False Then
MessageBox.Show("Please enter a positive numeric value for Exam3!")
Exit Sub
End If
'check for blanks
If (txtHomeworkGrade.Text) = "" Then
MessageBox.Show("Please enter Homework Grade!")
Exit Sub
End If
'check for numerics
If IsNumeric(txtHomeworkGrade.Text) = False Then
MessageBox.Show("Please enter a numeric positive value for Homework Grade!")
Exit Sub
End If
'check for blanks
If (txtPeerReviewGrade.Text) = "" Then
MessageBox.Show("Please enter a Peer Review Grade!")
Exit Sub
End If
'check for numerics
If IsNumeric(txtPeerReviewGrade.Text) = False Then
MessageBox.Show("Please enter a numeric positive value for Peer Review Grade!")
Exit Sub
End If
'check for blanks
If (txtLanguageReferenceGrade.Text) = "" Then
MessageBox.Show("Please enter a Language Reference Grade!")
Exit Sub
End If
'check for numerics
If IsNumeric(txtLanguageReferenceGrade.Text) = False Then
MessageBox.Show("Please enter a numeric positive value for Language Reference Grade!")
Exit Sub
End If
'check for blanks
If (txtFinalProjectGrade.Text) = "" Then
MessageBox.Show("Please enter a Final Project Grade!")
Exit Sub
End If
'check for numerics
If IsNumeric(txtFinalProjectGrade.Text) = False Then
MessageBox.Show("Please enter a numeric positive value for Final Project Grade!")
Exit Sub
End If
'convert data types
decExam1Grade = Convert.ToDecimal(txtExam1Grade.Text)
decExam2Grade = Convert.ToDecimal(txtExam2Grade.Text)
decExam3Grade = Convert.ToDecimal(txtExam3Grade.Text)
decHomeworkGrade = Convert.ToDecimal(txtHomeworkGrade.Text)
decPeerReviewGrade = Convert.ToDecimal(txtPeerReviewGrade.Text)
decLanguageReferenceGrade = Convert.ToDecimal(txtLanguageReferenceGrade.Text)
decFinalProjectGrade = Convert.ToDecimal(txtFinalProjectGrade.Text)
mdecFinalNumericGrade = (decExam1Grade * EXAM1GRADE_WEIGHT) + _
(decExam2Grade * EXAM2GRADE_WEIGHT) + _
(decExam3Grade * EXAM3GRADE_WEIGHT) + _
(decHomeworkGrade * HOMEWORKGRADE_WEIGHT) + _
(decPeerReviewGrade * HOMEWORKPEERREVIEW_WEIGHT) + _
(decLanguageReferenceGrade + LANGUAGEQUICKREFERENCE_WEIGHT) + _
(decFinalProjectGrade + FINALPROJECT_WEIGHT)
'check for 0 or positive
If decExam1Grade < 0 Then
MessageBox.Show("Please enter a positive value or zero for Exam 1!")
Exit Sub
End If
'check for 0 or positive
If decExam2Grade < 0 Then
MessageBox.Show("Please enter a positive value or zero for Exam 2!")
Exit Sub
End If
'check for 0 or positive
If decExam3Grade < 0 Then
MessageBox.Show("Please enter a positive value or zero for Exam 3!")
Exit Sub
End If
'check for 0 or positive
If decHomeworkGrade < 0 Then
MessageBox.Show("Please enter a positive value or zero for Homework Grade!")
Exit Sub
End If
'check for 0 or positive
If decPeerReviewGrade < 0 Then
MessageBox.Show("Please enter a positive value or zero for Peer Review Grade!")
Exit Sub
End If
'check for 0 or positive
If decLanguageReferenceGrade < 0 Then
MessageBox.Show("Please enter a positive value or zero for Language Reference!")
Exit Sub
End If
'check for 0 or positive
If decFinalProjectGrade < 0 Then
MessageBox.Show("Please enter a positive value or zero for Final Project Grade!")
Exit Sub
End If
'make sure values are less than 100
If decExam1Grade > 100 Then
MessageBox.Show("Please enter a value thats 100 or less!")
End If
If decExam2Grade > 100 Then
MessageBox.Show("Please enter a value thats 100 or less!")
End If
If decExam3Grade > 100 Then
MessageBox.Show("Please enter a value thats 100 or less!")
End If
If decHomeworkGrade > 100 Then
MessageBox.Show("Please enter a value thats 100 or less!")
End If
If decPeerReviewGrade > 100 Then
MessageBox.Show("Please enter a value thats 100 or less!")
End If
If decLanguageReferenceGrade > 100 Then
MessageBox.Show("Please enter a value thats 100 or less!")
End If
If decFinalProjectGrade > 100 Then
MessageBox.Show("Please enter a value thats 100 or less!")
End If
'Determine grade per letter
Select Case decpercent
Case Is >= 89.5D
mstrFinalLetterGrade = "A"
mintStudentsWithAs += 1
Case Is >= 79.5D
mstrFinalLetterGrade = "B"
Case Is >= 69.5D
mstrFinalLetterGrade = "C"
Case Is >= 59.5D
mstrFinalLetterGrade = "D"
Case Else
mstrFinalLetterGrade = "F"
mintStudentsWithFs += 1
End Select
lblFinalLetterGrade.Text = mstrFinalLetterGrade
'display outputs
lblFinalNumericGrade.Text = mdecFinalNumericGrade.ToString("f2")
End Sub
Private Sub btnClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClear.Click
'clear the texboxes and labels
txtExam1Grade.Clear()
txtExam2Grade.Clear()
txtExam3Grade.Clear()
txtHomeworkGrade.Clear()
txtPeerReviewGrade.Clear()
txtLanguageReferenceGrade.Clear()
txtFinalProjectGrade.Clear()
lblFinalLetterGrade.Text = ""
lblFinalNumericGrade.Text = ""
'setcursor back to top textbox
txtExam1Grade.Focus()
End Sub
Private Sub btnReset_Click(ByVal sende As System.Object, ByVal e As System.EventArgs) Handles btnReset.Click
'reset module level variables
mdecFinalNumericGrade = 0
mstrFinalLetterGrade = ""
mintStudentsWithAs = 0
mintStudentsWithFs = 0
End Sub
Private Sub btnExit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnExit.Click
'close the form
End
End Sub
Private Sub frmGradeCalculator_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
End Sub
End Class

Answer 1

Your final grade total is wrong because you're not multiplying the language presentation and final project by their weights, but adding the weight to the score:
Exam1 = 82 * .15 = 12.3
Exam2 = 87 * .20 = 17.4
Exam3 = 91 * .20 = 18.2
Assignments = 94 * .20 = 18.8
Peer Review = 100 * .05 = 5
Language Presentation = 90 + .10 = 90.1
Final Project = 92 + .10 = 92.1
Notice the addition (rather than multiplication) on the last two values. The total is 253.9.
Change the last two calculations for medcFinalNumericGrade to:
(decLanguageReferenceGrade * LANGUAGEQUICKREFERENCE_WEIGHT) + _
(decFinalProjectGrade * FINALPROJECT_WEIGHT)
You will always get an "F" because decpercent is never assigned a value, and therefore the Else Case is executed. Either assign decpercent a value, or use mdecFinalNumericGrade.
For example:
Select Case mdecFinalNumericGrade
instead of
Select Case decpercent
Once you fix the Select Case, your counts should work (unless you reset the form).