Question

I created a small vb.net console app in visual studio 2008 trying to learn .net but my results show differently when I break in the code and press F11 to step through. If I do it this way, the results I expect to get show but if I don’t break into the code the results aren’t what I’m expecting.

Basically everytime I click a button i want to write four numbers that are random. If I break into the code, these show random numbers i.e. 1 3 4 3 but if i don’t break into the code. my numbers are all the same i.e. 1 1 1 1.

Here is my code, like I said I’m still learning so the logic is probably not correct.

Module Module1

Dim number1 As Integer = 0
Dim _DiceRolled As Boolean = False
Dim number2 As Integer = 0
Dim number3 As Integer = 0
Dim number4 As Integer = 0
Dim numberArray() As Integer = {number1, number2, number3, number4}

Sub Main()

    Dim quit As Boolean = False
    Dim cki As ConsoleKeyInfo
    Do While quit = False
        If diceRolled = False Then
            Console.WriteLine("Press any key to roll the dice...")

            cki = Console.ReadKey


            If cki.KeyChar <> "q" Then
                quit = False
            Else
                quit = True
                Exit Do
            End If

            roll()
            diceRolled = True

        Else
            Console.WriteLine("Press any key to roll the dice again...")
            cki = Console.ReadKey
            If cki.KeyChar <> "q" Then
                quit = False
            Else
                quit = True
                Exit Do
            End If

            roll()
        End If
    Loop
    Console.WriteLine(" Game is over!")
    Console.ReadKey()


End Sub


Private Sub roll()
    Dim newNumbers(4) As Integer
    Dim stringbuilder As String = ""
    Console.Write(" New numbers : ")
    Dim count As Integer = 0
    stringbuilder = ""

    For Each number As Integer In numberArray


        newNumbers(count) = (generateRandomNumber(number))
        stringbuilder += (newNumbers(count).ToString() + " ")
        count += 1

    Next
    Console.Write(stringbuilder)
End Sub

Private Function generateRandomNumber(ByVal number As Integer)
    Dim rand As New Random
    number = rand.Next(1, 5)
    Return number
End Function

Private Property diceRolled()
    Get
        Return _DiceRolled
    End Get
    Set(ByVal value)
        _DiceRolled = value
    End Set
End Property


End Module

Any ideas? Thanks

Answer 1

You’re making a new Random instance for each random number.

By default, Random creates a seed from the current time.
Your code runs fast enough that all of the Randoms get the same seed.

When you step through it, the steps add pauses between the Randoms, so they get different seeds.

You should reuse the same Random instance in a Shared field.