How do I convert this javascript line to c#?

Question

I understand the first part of the line, but I'm not sure what the part after the || does. Can anyone tell me how to convert this line to c#?

var g = grid[iy * gw + ix] || [];

Original source is here. http://www.dhteumeuleu.com/aqualibrium/source

Answer 1

It's the logical or, but basically equivalent to C#'s null-coalescing operator ?? . It resolves to the left, or the right if the left is false .

The one caveat is that, because of Javascript's dynamic typing, the situation isn't as clear-cut as in C#. The || forces the left-hand value to be converted to a bool, and there are various values that will end up being converted to false . For example, Javascript will evaluate all these as "other":

* false || 'other';
* 0 || 'other';
* '' || 'other';
* undefined || 'other';

Answer 2

As commented || is equivalent to c#'s to the coalesce operator ??. And [] is an empty array.

In this case grid is an array of arrays of Particles. The C# equivalent code would be:

// Particle[][] grid = ...

Particle[] g = grid[iy * gw + ix] ?? new Particle[];