Having fun with custom collections!

Imports Alphabet

Public Class frmAlphabet

	Private _alphabet As WesternAlphabet

	Private Sub frmAlphabet_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
		_alphabet = New WesternAlphabet
	End Sub

	Private Sub btnGetAlphabet_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGetAlphabet.Click
		' Clear the Text of the Control.
		txtAlphabet.Text = String.Empty

		' Get the count of characters in the alphabet.
		' Notice that Count is an Extension Method!
		Dim count As Integer = _alphabet.Count
		For i As Integer = 0 To count - 2
			txtAlphabet.Text += _alphabet(i) & ", "
		Next
		' Omit the comma after the last character.
		txtAlphabet.Text += _alphabet(count - 1)
	End Sub

	Private Sub txtIndex_Validating(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles txtIndex.Validating
		Dim index As Integer
		If Integer.TryParse(txtIndex.Text, index) AndAlso index >= 0 Then
			errorProvider.SetError(txtIndex, String.Empty)
		Else
			errorProvider.SetError(txtIndex, "Please provide a valid zero-based index.")
			e.Cancel = True
		End If
	End Sub

	Private Sub btnGetChar_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGetChar.Click
		' Show the character at the specified index.
		' The Text in txtIndex has already been validated.
		If txtIndex.Text <> String.Empty Then
			txtChar.Text = _alphabet(CInt(txtIndex.Text))
		End If
	End Sub

End Class