TakeWhile using query syntax

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.

Answer 2

There's no built in syntax for this in LINQ. Besides, writing it in LINQ would be more verbose and wouldn't really aid clarity, so there's no real need in this case.

Also, you should use Take rather than TakeWhile here.