[2005/2008]Generating A Sudoku grid

[JuggaloBrotha]

Here's the class in it's entirety:

Option Explicit On
Option Strict On

Friend Class SudokuBoard

    Private WithEvents bw As New System.ComponentModel.BackgroundWorker
    Private m_TheBoard(8I, 8I) As Integer
    Private m_Numbers(8, 8) As List(Of Integer)
    Private Rand As New Random

    Friend Event BoardGenerated(ByVal TheBoard(,) As Integer)

#Region " Constructors "
    Friend Sub New()
        Me.GenerateBoard()
    End Sub
#End Region
#Region " GenerateBoard "
    Friend Sub GenerateBoard()
        Me.bw.RunWorkerAsync()
    End Sub

    Private Sub bw_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles bw.DoWork
        Dim ValidBoard As Boolean = False
        While ValidBoard = False
            ValidBoard = GenerateTheBoard()
        End While
    End Sub

    Private Sub bw_RunWorkerCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles bw.RunWorkerCompleted
        Dim Copy(8, 8) As Integer
        For x As Integer = 0I To 8I
            For y As Integer = 0I To 8I
                Copy(x, y) = m_TheBoard(x, y)
            Next y
        Next x
        RaiseEvent BoardGenerated(Copy)
    End Sub
#End Region
#Region " GenerateTheBoard "
    Private Function GenerateTheBoard() As Boolean
        'Code from JohnH
        Call ResetBoard()
        'try fill a board
        Dim fillcount As Integer = 0
        Do Until fillcount = 81
            'find cell with least available options
            Dim lowestAvailable As Integer = 10
            Dim cellref As Point = Point.Empty
            For x As Integer = 0 To 8
                For y As Integer = 0 To 8
                    If m_TheBoard(x, y) = 0 Then 'only include empty cells in search
                        Dim availCount As Integer = m_Numbers(x, y).Count
                        If availCount = 0 Then
                            Return False  'hit a dead end
                        ElseIf availCount < lowestAvailable Then
                            lowestAvailable = availCount
                            cellref = New Point(x, y)
                        End If
                    End If
                Next y
            Next x
            'fill that cell           
            Dim available As List(Of Integer) = m_Numbers(cellref.X, cellref.Y)
            If available.Count = 1 Then
                m_TheBoard(cellref.X, cellref.Y) = available(0)
            Else
                m_TheBoard(cellref.X, cellref.Y) = available(Rand.Next(0, available.Count))
            End If
            RemoveAvailable(cellref.X, cellref.Y)
            fillcount += 1
        Loop
        Return True 'valid solution
    End Function
#End Region
#Region " Friend Methods "
    Friend Sub ClearBoard()
        For x As Integer = 0I To 8I
            For y As Integer = 0I To 8I
                m_TheBoard(x, y) = 0I
            Next y
        Next x
    End Sub
#End Region
#Region " ResetBoard "
    Private Sub ResetBoard()
        'Code from JohnH
        For x As Integer = 0 To 8
            For y As Integer = 0 To 8
                m_Numbers(x, y) = New List(Of Integer)
                m_Numbers(x, y).AddRange(New Integer() {1, 2, 3, 4, 5, 6, 7, 8, 9})
                m_TheBoard(x, y) = 0
            Next y
        Next x
    End Sub
#End Region
#Region " RemoveAvailable "
    Private Sub RemoveAvailable(ByVal x As Integer, ByVal y As Integer)
        'Code from JohnH
        Dim value As Integer = m_TheBoard(x, y)
        'remove from column and row
        For xx As Integer = 0 To 8
            m_Numbers(xx, y).Remove(value)
        Next xx
        For yy As Integer = 0 To 8
            m_Numbers(x, yy).Remove(value)
        Next yy
        'remove from one of the 3x3 sections
        Dim xxx As Integer = (x \ 3) * 3
        Dim yyy As Integer = (y \ 3) * 3
        For xx As Integer = xxx To xxx + 2
            For yy As Integer = yyy To yyy + 2
                m_Numbers(xx, yy).Remove(value)
            Next yy
        Next xx
    End Sub
#End Region
End Class

To use it, simply make a new instance and handle the BoardGenerated() event. Which gives you a 9x9 grid of the entire thing.

    Private WithEvents m_Sudoku As SudokuBoard
    Private m_ActualBoard(8, 8) As Integer

    Private Sub GenerateBoard()
        m_Sudoku = New SudokuBoard
    End Sub

    Private Sub m_Sudoku_BoardGenerated(ByVal TheBoard(,) As Integer) Handles m_Sudoku.BoardGenerated
        For X As Integer = 0 To 8
            For Y As Integer = 0 To 8
                m_ActualBoard(X, Y) = TheBoard(X, Y)
            Next Y
        Next X
    End Sub