??= In C#

C# has had the null coalescing operator ?? For a while now. It lets you condense

if (x = null)
{
  y = x;
}
else
{
  y = otherThing;
}

into

y = x ?? otherThing;

It’s a great tool for both condensing code and improving readability.

I found out recently though that C# 8.0 expanded on that idea. There is a common design pattern of caching a computed value in a variable so you only have to compute it once.

private int? _Example = null;
Public int? Example
{
  get
  {
    if (_Example == null)
    {
      _Example = ComputeExample();
    }
    return _Example;
  }
}

This isn’t that bad. It works. But it’s tedious to write (especially on mobile like I am now for this post). Enter the null coalescing assignment operator.

private int? _Example = null;
Public int? Example
{
  get
  {
    return _Example ??= ComputeExample();
  }
}

I love it!