If you want to iterate over every item in the array as if it were a flattened array, you can just do:
foreach (int i in array) {
Console.Write(i);
}
which would print 123456
If you want to be able to know the x and y indexes as well, you'll need to do:
for (int x = 0; x < array.GetLength(0); x += 1) {
for (int y = 0; y < array.GetLength(1); y += 1) {
Console.Write(array[x, y]);
}
}
Alternatively you could use a jagged array instead (an array of arrays):
int[][] array = new int[2][] { new int[3] {1, 2, 3}, new int[3] {4, 5, 6} };
foreach (int[] subArray in array) {
foreach (int i in subArray) {
Console.Write(i);
}
}
or
int[][] array = new int[2][] { new int[3] {1, 2, 3}, new int[3] {4, 5, 6} };
for (int j = 0; j < array.Length; j += 1) {
for (int k = 0; k < array[j].Length; k += 1) {
Console.Write(array[j][k]);
}
}