SudokuGen lngr -TizzyT

Module SudokuGen
    Private Rnd As New Random
    Private Board(8, 8) As Cell
    Private Blks(,,) As Byte = _
    {{{0, 0}, {0, 1}, {0, 2}, {1, 0}, {1, 1}, {1, 2}, {2, 0}, {2, 1}, {2, 2}}, _
    {{0, 3}, {0, 4}, {0, 5}, {1, 3}, {1, 4}, {1, 5}, {2, 3}, {2, 4}, {2, 5}}, _
    {{0, 6}, {0, 7}, {0, 8}, {1, 6}, {1, 7}, {1, 8}, {2, 6}, {2, 7}, {2, 8}}, _
    {{3, 0}, {3, 1}, {3, 2}, {4, 0}, {4, 1}, {4, 2}, {5, 0}, {5, 1}, {5, 2}}, _
    {{3, 3}, {3, 4}, {3, 5}, {4, 3}, {4, 4}, {4, 5}, {5, 3}, {5, 4}, {5, 5}}, _
    {{3, 6}, {3, 7}, {3, 8}, {4, 6}, {4, 7}, {4, 8}, {5, 6}, {5, 7}, {5, 8}}, _
    {{6, 0}, {6, 1}, {6, 2}, {7, 0}, {7, 1}, {7, 2}, {8, 0}, {8, 1}, {8, 2}}, _
    {{6, 3}, {6, 4}, {6, 5}, {7, 3}, {7, 4}, {7, 5}, {8, 3}, {8, 4}, {8, 5}}, _
    {{6, 6}, {6, 7}, {6, 8}, {7, 6}, {7, 7}, {7, 8}, {8, 6}, {8, 7}, {8, 8}}}
    Public Sub Main()
        While True
            For x = 0 To 8
                For y = 0 To 8
                    Board(x, y) = New Cell
                Next
            Next
            Dim ValidBlks As List(Of Byte) = New Byte() {0, 1, 2, 3, 4, 5, 6, 7, 8}.ToList
            Dim Retry As Boolean = False
            Do Until ValidBlks.Count = 0
                Dim ValidCells As List(Of Byte) = New Byte() {0, 1, 2, 3, 4, 5, 6, 7, 8}.ToList
                Dim B As Byte = ValidBlks(Rnd.Next(ValidBlks.Count))
                ValidBlks.Remove(B)
                Do Until ValidCells.Count = 0
                    Dim C As Byte = ValidCells(Rnd.Next(ValidCells.Count))
                    Dim X As Byte = Blks(B, C, 0), Y As Byte = Blks(B, C, 1), N As Byte = 0
                    If Board(X, Y).Process(N) Then
                        Retry = True
                        Exit Do
                    Else
                        ValidCells.Remove(C)
                        For i = 0 To 8
                            Board(X, i).ValidNbrs.Remove(N) : Board(i, Y).ValidNbrs.Remove(N)
                            Board(Blks(B, i, 0), Blks(B, i, 1)).ValidNbrs.Remove(N)
                        Next
                    End If
                Loop
                If Retry Then Exit Do
            Loop
            If Not Retry Then Exit While
        End While
        Console.Write(vbCrLf)
        For X = 0 To 2
            Console.Write(" ")
            For Y = 0 To 2 : Console.Write(Board(X, Y).Value & " ") : Next
            Console.Write(" ")
            For Y = 3 To 5 : Console.Write(Board(X, Y).Value & " ") : Next
            Console.Write(" ")
            For Y = 6 To 8 : Console.Write(Board(X, Y).Value & " ") : Next
            Console.Write(vbCrLf)
        Next
        Console.Write(vbCrLf)
        For X = 3 To 5
            Console.Write(" ")
            For Y = 0 To 2 : Console.Write(Board(X, Y).Value & " ") : Next
            Console.Write(" ")
            For Y = 3 To 5 : Console.Write(Board(X, Y).Value & " ") : Next
            Console.Write(" ")
            For Y = 6 To 8 : Console.Write(Board(X, Y).Value & " ") : Next
            Console.Write(vbCrLf)
        Next
        Console.Write(vbCrLf)
        For X = 6 To 8
            Console.Write(" ")
            For Y = 0 To 2 : Console.Write(Board(X, Y).Value & " ") : Next
            Console.Write(" ")
            For Y = 3 To 5 : Console.Write(Board(X, Y).Value & " ") : Next
            Console.Write(" ")
            For Y = 6 To 8 : Console.Write(Board(X, Y).Value & " ") : Next
            Console.Write(vbCrLf)
        Next
    End Sub
    Public Class Cell
        Public Value As Byte = 0
        Public ValidNbrs As List(Of Byte) = New Byte() {1, 2, 3, 4, 5, 6, 7, 8, 9}.ToList
        Public Function Process(ByRef SelectedNbr As Byte) As Boolean
            If ValidNbrs.Count = 0 Then Return True
            Value = ValidNbrs(Rnd.Next(ValidNbrs.Count))
            SelectedNbr = Value
            Return False
        End Function
    End Class
End Module