Array like php to C#

I got the following thing in php, how do you write this for arrays in C#?

$x = 100;
$y = 50;
for($i = 0; $i < $x; $i++) {
	for($j = 0; $j < $y; $j++) {
		$array[$i][$j] = new Tile();
	}
}

It will be used like:

if($build == Unit::TANK) {
	if($array[4][10]->isType(Tile::LAND)) && $array[4][10]->hasFactory($owner)) {
		$array[4][10]->addObject(Unit::TANK, $owner);
	}
}

I've tried several things, but it seems php is the only language that uses "arrays" which you can index yourself...