Shuffle extension method throws on empty enumerable

[abeham]

It throws an IndexOutOfRangeException because the 0th element is returned even if the length of array is 0.

[abeham]

Following options:

1. Query for an empty enumerable and throw an ArgumentException instead of an IndexOutOfRangeException
2. Return an empty enumerable

I went with option 2) because it leads to cleaner code at the caller site. Option one requires the caller to check on that condition which leads to evaluating a condition twice or requires two calls to ToList().

1)

var aList = Enumerable.Range(0, count).Where(x => SomeCondition(x)).ToList();
if (aList.Count == 0) {
  // handle empty case
} else {
  aList = aList.Shuffle().ToList();
}

// or

IList<int> aList = null;
if (Enumerable.Range(0, count).Any(x => SomeCondition(x))) {
  aList = Enumerable.Range(0, count).Where(x => SomeCondition(x)).Shuffle().ToList();
} else {
  // handle empty case
}

2)

  var aList = Enumerable.Range(0, count).Where(x => SomeCondition(x)).Shuffle().ToList();
  if (aList.Count == 0) {
    // handle empty case
  }

[abeham]

r14522: check if enumerable contains at least one element before returning the first element

[gkronber]

Reviewed r14522

[abeham]

r14669: merged r14522 to stable