C# 2d array value replace

Question

I've created an array like this:

int[,] grid = new int[9, 9];

        Random randomNumber = new Random();
        var rowLength = grid.GetLength(0);
        var colLength = grid.GetLength(1);
        for (int row = 0; row < rowLength; row++)
        {
            for (int col = 0; col < colLength; col++)
            {
                grid[row, col] = randomNumber.Next(6);


            }

        }

This will result in an 2d array 9x9 which is filled with random numbers. example:

5 5 0 0 4 3 3 4 5
2 0 5 5 2 1 2 0 4
4 0 2 0 2 4 3 5 4
0 3 4 3 1 2 4 1 1
5 4 1 3 3 0 4 3 4
0 2 3 3 1 2 0 1 5
2 4 3 1 2 5 4 3 1
0 4 5 3 1 1 0 3 1
2 1 2 2 2 4 0 3 2

Now comes the real question: How can I make the zeros "disappear"(the zeros would be replaced with the values above them, or the zeros would move up against the top)? Obviously the zeros at the top row do not have any values above them so there would have to be created a new random number. Also randomNumber.Next(6)+1 is not an option this time around. I have tried this,but to no use:

 foreach(int z in grid)
        {
        if(z==0)
        {
        if(col>0)
        {
        int a=grid[col,row];
        int b=grid[col-1,row];
        a=b;
        b=a;



        }
        else
        {
            int a = grid[col, row];
        Random randomNumber= new Random();
        a = randomNumber.Next(6) + 1;
        }



        }
        }   

EDIT: Example in a 3x3: initial grid:

1 3 5

0 5 3

3 4 0

after:

R 3 R

1 5 5

3 4 3

R=new randomNumber which is not 0

Answer 1

I understand that this is what you want : (the zeros would be replaced with the values above them, or the zeros would move up against the top)

    int[,] grid = new int[9, 9];
    Random randomNumber = new Random();
    var rowLength = grid.GetLength(0);
    var colLength = grid.GetLength(1);
    for (int row = 0; row < rowLength; row++)
    {
        for (int col = 0; col < colLength; col++)
        {
            grid[row, col] = randomNumber.Next(6);
            if(grid[row,col) == 0)
            {
                if(row == 0)
                {
                    while(true)
                    {
                       grid[row,col] = randomNumber.Next(6);
                       if(grid[row,col] == 0)
                          continue;
                       else
                          break;
                    }
                }
                else
                {
                    grid[row,col] = grid[row-1,col];
                }
            }                 
        }

    }

Edit : Sorry, I checked to code after you show me output and realised that I forgot to check if the entry is equal to 0 or not :)

Answer 2

Basically you are looking to get a Random number between 1 and 6?

For that you can use the Random.Next(int minValue, int maxValue) method.

Random randomNumber = new Random();
randomNumer.Next(1, 6);

Also, when working with random you should never re-seed inside of the loop. Instantiate the Random object before the loop, then use it. Your first example was good, but not the second one.

Answer 3

I briefly tested this, and it appears to do what you want:

        int[,] grid = new int[3, 3];

        grid[0, 0] = 1;
        grid[0, 1] = 2;
        grid[0, 2] = 3;
        grid[1, 0] = 0;
        grid[1, 1] = 5; 
        grid[1, 2] = 6; 
        grid[2, 0] = 0;
        grid[2, 1] = 8; 
        grid[2, 2] = 9;

        Random randomNumber = new Random();
        var rowLength = grid.GetLength(0);
        var colLength = grid.GetLength(1);

        //for (int row = 0; row < rowLength; row++)
        //{
        //    for (int col = 0; col < colLength; col++)
        //    {
        //        grid[row, col] = randomNumber.Next(6);
        //        if (row == 1 && col == 0)
        //            grid[row, col] = 0;
        //        if (row == 2 && col == 0)
        //            grid[row, col] = 0;
        //    }
        //}

        //  Now, we have the grid with 0's, time to play Tetris with the 0's.
        for (int row = rowLength - 1; row >= 0; row--)
        {
            for (int col = 0; col < colLength; col++)
            {
                if (grid[row, col] == 0)
                {
                    for (int currentRow = row; currentRow >= 0; currentRow--)
                    {
                        if (currentRow == 0)
                            grid[currentRow, col] = randomNumber.Next(1, 6);
                        else
                        {
                            grid[currentRow, col] = grid[currentRow - 1, col];
                            if (grid[currentRow, col] == 0)  //  There was a 0 above our 0.
                            {
                                bool replaced = false;
                                for (int numberOfRowsAbove = 1; numberOfRowsAbove <= currentRow; numberOfRowsAbove++)
                                {
                                    if (grid[currentRow - numberOfRowsAbove, col] != 0)
                                    {
                                        grid[currentRow, col] = grid[currentRow - numberOfRowsAbove, col];
                                        replaced = true;
                                    }
                                }
                                if (!replaced)
                                    grid[currentRow, col] = randomNumber.Next(1, 6);

                            }
                        }
                    }
                }

            }

        }