throw expressions with C# 7

ThrowExpressions.cs

// C# 6
private readonly IBooksService _booksService;
public BookController(BooksService booksService)
{
  if (booksService == null)
  {  
    throw new ArgumentNullException(nameof(b));
  }

  _booksService = booksService;
}

// C# 7
private readonly IBooksService _booksService;
public BookController(BooksService booksService)
{
  _booksService = booksService ?? throw new ArgumentNullException(nameof(b));
}