Dynamic Arrays in VB - vb.net

Question

Struggling student here... I've been asked to find the min, max and mid-point value. However, I cannot figure this out; arrays/data storage is 3 chapters away. So, I'm hoping someone could help me out with this conundrum.
-I need to get the data from an individual element within an array in decimal. Any ideas? I've largely been unsuccessful with the 'array.getvalue' method & with the 'array.min' methods.
Dim numberOfInvoices As Integer
Dim totalOfInvoices As Decimal
Dim invoiceAverage As Decimal
Private Sub BtnCalculate_Click(sender As Object, e As EventArgs) Handles btnCalculate.Click
Dim subtotal As Decimal = CDec(txtEnterSubtotal.Text)
Dim discountPercent As Decimal = 0.25D
Dim discountAmount As Decimal = Math.Round(subtotal * discountPercent, 2)
Dim invoiceTotal As Decimal = subtotal - discountAmount
Dim minimum, maximum, middle, i As Decimal
Dim array(1) As Decimal
Dim midpoint As Integer
txtSubtotal.Text = FormatCurrency(subtotal)
txtDiscountPercent.Text = FormatPercent(discountPercent, 1)
txtDiscountAmount.Text = FormatCurrency(discountAmount)
txtTotal.Text = FormatCurrency(invoiceTotal)
numberOfInvoices += 1
totalOfInvoices += invoiceTotal
invoiceAverage = totalOfInvoices / numberOfInvoices
For i = 0 To numberOfInvoices - 1
array(i) = i
ReDim Preserve array(0 To numberOfInvoices - 1)
Next i
If numberOfInvoices = 1 Then
minimum = totalOfInvoices
middle = totalOfInvoices
maximum = totalOfInvoices
End If
If numberOfInvoices > 1 Then
midpoint = numberOfInvoices / 2
middle = array.GetValue(midpoint)
For Each i In array
If i < UBound(array) - 1 Then If array(i) > array(i + 1) Then maximum = array(i)
If i < UBound(array) - 1 Then If array(i) < array(i + 1) Then minimum = array(i)
Next i
End If
txtLargestInvoice.Text = maximum.ToString
txtSmallestInvoice.Text = minimum.ToString
txtMidPoint.Text = middle.ToString
txtNumberOfInvoices.Text = numberOfInvoices.ToString
txtTotalOfInvoices.Text = FormatCurrency(totalOfInvoices)
txtInvoiceAverage.Text = FormatCurrency(invoiceAverage)
txtEnterSubtotal.Text = ""
txtEnterSubtotal.Select()
End Sub
Private Sub BtnClearTotals_Click(sender As Object,
e As EventArgs) Handles btnClearTotals.Click
numberOfInvoices = 0
totalOfInvoices = 0
invoiceAverage = 0
txtNumberOfInvoices.Text = ""
txtTotalOfInvoices.Text = ""
txtInvoiceAverage.Text = ""
txtEnterSubtotal.Select()
End Sub
Private Sub BtnExit_Click(sender As Object,
e As EventArgs) Handles btnExit.Click
Me.Close()
End Sub

Answer 1

Comments and explanations in-line
Private Sub OPCode2()
'You can declare and initialize an array in one line
Dim arr() As Double = {13.5, 18.0, 6.2, 11.8, 13.6}
'Just check intellisense for a list of methods and properties of arrays
Dim myAverage As Double = arr.Average()
Dim myMin As Double = arr.Min
Dim myMax As Double = arr.Max
Dim myMedian As Double
'The original array is lost when .Sort is applied
Array.Sort(arr)
Dim myLength As Integer = arr.Length
'If the lenght of the array is even you could also average
'the middle two values And return that number which
'may not be a value in the original array
myMedian = arr(CInt(myLength / 2)) 'returns the higher of the middle two if length is even
'or the actual middle value in the sorted array
MessageBox.Show($" The Average value is {myAverage}
The Maximum value is {myMax}
The Minimum value is {myMin}
The Median value is {myMedian}")
End Sub