How to take Items from List in Visual Basic

Question

I am trying to take Items that I have already added to a list.

        Dim lista As New List(Of String)
        n = 2
        i = 0
        Do While i < n + 1
            Randomize()
            a = Int(Rnd() * 4) + 1
            If a = 1 Then
                lista.Add("1b")
            ElseIf a = 2 Then
                lista.Add("2b")
            ElseIf a = 3 Then
                lista.Add("3b")
            ElseIf a = 4 Then
                lista.Add("4b")
            End If
            i = i + 1
        Loop

Lets imagine that the list i got was {2b,4b,1b}. Now i want to know how to get lets say just 2b from the list as a first Item and then delete it from the list.

Answer 1

This would be a good place to use a Queue(Of ) .

Dim item As String

item = queuea.Dequeue

But List(Of ) has an indexer so you can just use it like an array:

Dim item As String

item = lista(0)
' Then remove the first item:
lista.RemoveAt(0)

Answer 2

Use the .net Random class instead of the old VB6 methods. Calling Random.Next(Interger1, Integer2) will return an Integer equal to or greater than Integer1 and less than Integer2 . Note that since the values are so limited there is a good chance of having duplicates in the list.

Although multiple ElseIf s will work, a Select Case is easier to read and less typing.

I put the contents of the list in a ListBox so we could see what was going on. I used the Remove method of List(Of T) then rebind the ListBox .

Private lista As New BindingList(Of String)
Private rand As New Random

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    BuildList()
    ListBox1.DataSource = lista
End Sub

Private Sub BuildList()
    Dim i = 0
    Dim a As Integer
    Do While i < 3 'since n never changes just use the literal value
        a = rand.Next(1, 5)
        Select Case a
            Case 1
                lista.Add("1b")
            Case 2
                lista.Add("2b")
            Case 3
                lista.Add("3b")
            Case 4
                lista.Add("4b")
        End Select
        i = i + 1
    Loop

End Sub

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click 'Remove from list
    lista.Remove(ListBox1.SelectedItem.ToString)
End Sub