Question

Having

public static IEnumerable<long> FibonacciNumbers() {
 long current = 0;
 long next = 1;

 while (true) {
  long previous = current;
  current = next ;
  next = previous + next;
  yield return current;
 }
}

I can get the first fibonacci numbers less that 100 with

var series = FibonacciNumbers().TakeWhile(num => num < 100);

Just being curious, how would I do that using query syntax ?

Answer 1

You wouldn’t – there’s nothing in C# query expressions that corresponds to TakeWhile (or Take, Skip, SkipWhile etc). C# query expressions are relatively limited, but cover the biggies:

• Select (via select and let)
• Where (via where)
• SelectMany (via secondary from clauses)
• OrderBy/ThenBy (and descending) (via orderby clauses)
• Join (via join clauses)
• GroupBy (via groupby clauses)
• GroupJoin (via join ... into clauses)

VB 9’s query support is a bit more extensive, but personally I like C#’s approach – it keeps the language relatively simple, but you can still do everything you want via dot notation.