I have two text boxes, submit button. and a dropdown list with the items(even, odd, and all). I want to calculate the sum of either all "Even", "Odd" or "All" numbers according the selection. In the code below, I have the "all" section working correctly but I'm trying to figure out a way to get the Even and Odd to work.

Some one suggested me to develope a good formula for determining whether a number is even or odd, then calling that from within the program as needed. I've tried that below with the IsEvenNumber function but got stuck. Any suggestions? Thanks

Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSubmit.Click
        If Me.ddlChoices.SelectedValue = "Even" Then
            Even_Numbers()
        End If
        If Me.ddlChoices.SelectedValue = "Odd" Then
            Odd_Numbers()
        End If
        If Me.ddlChoices.SelectedValue = "All" Then
            All_Numbers()
        End If
    End Sub


'suggestion from a friend
    Private Function IsEvenNumber(ByVal input As Integer) As Boolean
        IsEvenNumber = (input Mod 2 = 0)

        If input Mod 2 = 0 Then
            Return True
        Else
            Return False
        End If

    End Function




'sum of all
    Public Sub All_Numbers()
        Dim var As Integer
        Dim intcount As Integer
        Dim intcount2 As Integer

        intcount = CInt(txtOption1.Text)
        intcount2 = CInt(txtOption2.Text)
        var = 0

        Do While intcount <= intcount2

            var = var + intcount
            intcount = intcount + 1

        Loop

        Me.lblShow.Text = "The answer is:" & var
    End Sub



'sum of odd
    Public Sub Odd_Numbers()
        Dim var As Integer
        Dim intcount As Integer
        Dim intcount2 As Integer

        intcount = CInt(txtOption1.Text)
        intcount2 = CInt(txtOption2.Text)
        var = 0

        Do While intcount <= intcount2

            var = var + intcount
            intcount = intcount + 2

        Loop

        Me.lblShow.Text = "The answer is:" & var
    End Sub




'sum of even
    Public Sub Even_Numbers()
        Dim var As Integer
        Dim intcount As Integer
        Dim intcount2 As Integer

        intcount = CInt(txtOption1.Text)
        intcount2 = CInt(txtOption2.Text)
        var = 1

        Do While intcount <= intcount2

            var = var + intcount
            intcount = intcount + 2

        Loop

        Me.lblShow.Text = "The answer is:" & var
    End Sub

First thing is var is a reserved word. Don't use it as a variable.
Second, you went to the trouble making IsEvenNumber() but you don't call it.

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