OOPs.. I Don't have to do it again

Sudoku puzzles can be generated by a switching the rows and columns of a valid puzzle. The switch has to be done between the 123, 456 and 789 rows/columns. ie; 1 cannot be switched with 7 for example. A random pair can be generated and if a loop is run say 50 times, we get a new puzzle. Then the cells can be hidden again randomly. The following code generates the puzzle from a base character string which is converted to a 81 length Char array. The output is the solution as well as the puzzle with blank (or 0s)               Dim stdArray As String = "317849265245736891869512473456398712732164958981257634174925386693481527528673149"         Dim charArray() As Char = stdArray.ToCharArray         Dim rng As New Random         Dim m As Integer         Dim row1 As Integer         Dim row2 As Integer         Dim col1 As Integer         Dim col2 As Integer         Dim i As Integer         Dim cell1 As Integer         Dim cell2 As Integer         Dim tempC A