Do Until Loop checking for duplicates wont stop looping - vb.net

Question

I'm trying to do a Do Until Loop to check for duplicates in my combo box. It runs the loop but it never stops looping.
Dim i As Integer = 0
Dim flavors As Integer = flavorsComboBox.Items.Count
Do Until (i < flavors - 1)
If flavors = flavorsComboBox.Items.Count Then
MessageBox.Show("Flavor Already Exists!", "Error")
Else
flavorsComboBox.Items.Add(flavorsComboBox.Text)
End If
Loop

Answer 1

The condition of the loop looks at the i variable and the flavors variable:
Do Until (i < flavors - 1)
But those variables don't ever change at any point in the body of the loop:
If flavors = flavorsComboBox.Items.Count Then
MessageBox.Show("Flavor Already Exists!", "Error")
Else
flavorsComboBox.Items.Add(flavorsComboBox.Text)
End If
You need to add code to change one or both of those variables. But that's still the hard way to do this. Just use the Distinct() method:
Dim items = flavorsComboBox.Items.Distinct().ToArray()
flavorsComboBox.Items.Clear()
flavorsComboBox.Items.AddRange(items)

Answer 2

Here is a simple do until loop
Dim i as integer = 0
Dim flavors as Integer = 10
do until (i > flavors -1)
Console.WriteLine(i.ToString())
i = i +1
loop
Output
0
1
2
3
4
5
6
7
8
9
In your code:
do until (i < flavors - 1)
if i = 0 and flavors is the Count -1 when is 0 greater than count, to enter the condition of the loop.
The next omission is that you never change the value of condition variable of looping, to have an accurate evaluation of the condition to stop the loop.

Answer 3

Try this:
Option Strict On
Option Explicit On
Option Infer Off
Public Class Form1
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
If AddDistinct(flavorsComboBox, "test") Then
MsgBox("Item did not exist, so it was added.")
Else
MsgBox("Item already existed, so it was not added.")
End If
End Sub
Public Function AddDistinct(cboBox As ComboBox, value As Object) As Boolean
If cboBox.Items.IndexOf(value) = -1 Then cboBox.Items.Add(value) : Return True
Return False
End Function
End Class

Answer 4

You are not resetting the value of flavors
Try this:
Dim i As Integer = 0
Dim flavors As Integer = flavorsComboBox.Items.Count
Do Until (i < flavors - 1)
If flavors = flavorsComboBox.Items.Count Then
MessageBox.Show("Flavor Already Exists!", "Error")
Else
flavorsComboBox.Items.Add(flavorsComboBox.Text)
flavors = flavorsComboBox.Items.Count
End If
Loop