Shuffle the position of button controls on a page using an array and the random function

Category VB.Net Sub Category Utilities Bespoke

The purpose of this is to make a series of controls (in this case buttons) randomly appear on the page. Each button is still related to the same event but their position and caption text is changed to keep the same physical order e.g. A, B, C, D, E.

This is very useful in situations where you want to mix up buttons that are linked to questions in a test, so that the person taking the test cannot rely on the order of butons to help work out the answers. In the case where someone who has already taken the test, has told them the order to expect the answers.

In the aspx page:

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<div style="position:relative;">

    <asp:Button ID="btn1" runat="server" Text="1" ToolTip="1 orig" />
    <asp:Button ID="btn2" runat="server" Text="2" ToolTip="2 orig" />
    <asp:Button ID="btn3" runat="server" Text="3" ToolTip="3 orig" />
    <asp:Button ID="btn4" runat="server" Text="4" ToolTip="4 orig" />
    <asp:Button ID="btn5" runat="server" Text="5" ToolTip="5 orig" />
    
</div>

In the aspx.vb code behind page:

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Private btnHoriPos() As String = {"50", "100", "150", "200", "250"}

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

    shuffleButtons()
End Sub


Private Sub shuffleButtons()

    shuffle(btnHoriPos, 7)

    For i As Int32 = 1 To 5

        Dim btn As Button = DirectCast(FindControl(String.Concat("btn", i)), Button)
        'set the button positions based on shuffle
        btn.Attributes.Add("Style", String.Format("position:absolute; left:{0}px;", btnHoriPos(i - 1)))
        'set the text to be correct again after move
        fixButtonText(btn, btnHoriPos(i - 1))

    Next
End Sub


Private Sub shuffle(ByRef arrayToBeShuffled As Array, ByVal numberOfTimesToShuffle As Integer)

    Dim rndPosition As New Random(DateTime.Now.Millisecond)

    For i As Integer = 1 To numberOfTimesToShuffle
        For i2 As Integer = 1 To arrayToBeShuffled.Length
            swap(arrayToBeShuffled(rndPosition.Next(0, arrayToBeShuffled.Length)), arrayToBeShuffled(rndPosition.Next(0, arrayToBeShuffled.Length)))
        Next i2
    Next i
End Sub


Private Sub swap(ByRef arg1 As Object, ByRef arg2 As Object)

    Dim strTemp As String
    strTemp = arg1
    arg1 = arg2
    arg2 = strTemp
End Sub


Private Sub fixButtonText(ByRef btn As Button, ByVal position As Int32)
    '{"50", "100", "150", "200", "250"}

    Select Case position
        Case 50
            btn.Text = "A"
        Case 100
            btn.Text = "B"
        Case 150
            btn.Text = "C"
        Case 200
            btn.Text = "D"
        Case 250
            btn.Text = "E"
    End Select
End Sub