Moving objects inside arrays

Block[,] blocks = new Block[10,20];

blocks[x,y+1] = blocks[x,y];

blocks[x,y] = null;

blocks[x,y+1] = blocks[x,y];

blocks[x,y] = null;

/* assumes blocks[0] is the bottom row and you build upwards
   towards blocks.Count */
List<Block[]> blocks = new List<Block[]>();

void EatBottomRow()
{
    blocks.RemoveAt(0);
}