Old question but new questioners at all time.
According to source of System.Linq.Enumerable, ToList just return a new List(source), while ToArray use a new Buffer<T>(source).ToArray() to return a T[].
About memory allocation:
While running on an IEnumerable<T> only object, ToArray do allocate memory one more time than ToList. But you do not have to care about it in most cases, because GC will do the garbage collection when needed.
About the runtime efficient:
Those who are questioning this question can run the following code on your own machine, and you'll get your answer.
class PersonC
{
public Guid uuid;
public string name;
public int age;
public bool sex;
public DateTime BirthDay;
public double weight;
}
struct PersonS
{
public Guid uuid;
public string name;
public int age;
public bool sex;
public DateTime BirthDay;
public double weight;
}
class PersonT<T> : IEnumerable<T>
{
private List<T> items;
public PersonT(IEnumerable<T> init)
{
items = new List<T>(init);
}
public IEnumerator<T> GetEnumerator() => items.GetEnumerator();
IEnumerator IEnumerable.GetEnumerator() => items.GetEnumerator();
}
private IEnumerable<PersonC> C(int count)
{
for (var i = 0; i < count; ++i)
{
var guid = Guid.NewGuid();
var guidBytes = guid.ToByteArray(); //16 bytes
yield return new PersonC
{
uuid = guid,
name = guid.ToString(),
age = guidBytes[0] ^ guidBytes[7],
sex = guidBytes[14] % 2 == 0,
BirthDay = DateTime.Now.AddDays(-guidBytes[11] * 18),
weight = guidBytes[12] * 100
};
}
}
private IEnumerable<PersonS> S(int count)
{
for (var i = 0; i < count; ++i)
{
var guid = Guid.NewGuid();
var guidBytes = guid.ToByteArray(); //16 bytes
yield return new PersonS
{
uuid = guid,
name = guid.ToString(),
age = guidBytes[0] ^ guidBytes[7],
sex = guidBytes[14] % 2 == 0,
BirthDay = DateTime.Now.AddDays(-guidBytes[11] * 18),
weight = guidBytes[12] * 100
};
}
}
private void MakeLog(string test, List<long> log) =>
Console.WriteLine("{0} {1} ms -> [{2}]",
test,
log.Average(),
string.Join(", ", log)
);
private void Test1(int times, int count)
{
var test = Enumerable.Range(1, times).ToArray();
MakeLog("C.ToList", test.Select(o =>
{
var sw = new Stopwatch();
GC.Collect();
sw.Start();
var ret = C(count).ToList();
sw.Stop();
return sw.ElapsedMilliseconds;
}).ToList());
MakeLog("C.ToArray", test.Select(o =>
{
var sw = new Stopwatch();
GC.Collect();
sw.Start();
var ret = C(count).ToArray();
sw.Stop();
return sw.ElapsedMilliseconds;
}).ToList());
MakeLog("S.ToList", test.Select(o =>
{
var sw = new Stopwatch();
GC.Collect();
sw.Start();
var ret = S(count).ToList();
sw.Stop();
return sw.ElapsedMilliseconds;
}).ToList());
MakeLog("S.ToArray", test.Select(o =>
{
var sw = new Stopwatch();
GC.Collect();
sw.Start();
var ret = S(count).ToArray();
sw.Stop();
return sw.ElapsedMilliseconds;
}).ToList());
}
private void Test2(int times, int count)
{
var test = Enumerable.Range(1, times).ToArray();
var dataC1 = new PersonT<PersonC>(C(count));
var dataS1 = new PersonT<PersonS>(S(count));
MakeLog("C1.ToList", test.Select(o =>
{
var sw = new Stopwatch();
GC.Collect();
sw.Start();
var ret = dataC1.ToList();
sw.Stop();
return sw.ElapsedMilliseconds;
}).ToList());
MakeLog("C1.ToArray", test.Select(o =>
{
var sw = new Stopwatch();
GC.Collect();
sw.Start();
var ret = dataC1.ToArray();
sw.Stop();
return sw.ElapsedMilliseconds;
}).ToList());
MakeLog("S1.ToList", test.Select(o =>
{
var sw = new Stopwatch();
GC.Collect();
sw.Start();
var ret = dataS1.ToList();
sw.Stop();
return sw.ElapsedMilliseconds;
}).ToList());
MakeLog("S1.ToArray", test.Select(o =>
{
var sw = new Stopwatch();
GC.Collect();
sw.Start();
var ret = dataS1.ToArray();
sw.Stop();
return sw.ElapsedMilliseconds;
}).ToList());
}
private void Test3(int times, int count)
{
var test = Enumerable.Range(1, times).ToArray();
var dataC2 = (ICollection<PersonC>) new List<PersonC>(C(count));
var dataS2 = (ICollection<PersonS>) new List<PersonS>(S(count));
MakeLog("C2.ToList", test.Select(o =>
{
var sw = new Stopwatch();
GC.Collect();
sw.Start();
var ret = dataC2.ToList();
sw.Stop();
return sw.ElapsedMilliseconds;
}).ToList());
MakeLog("C2.ToArray", test.Select(o =>
{
var sw = new Stopwatch();
GC.Collect();
sw.Start();
var ret = dataC2.ToArray();
sw.Stop();
return sw.ElapsedMilliseconds;
}).ToList());
MakeLog("S2.ToList", test.Select(o =>
{
var sw = new Stopwatch();
GC.Collect();
sw.Start();
var ret = dataS2.ToList();
sw.Stop();
return sw.ElapsedMilliseconds;
}).ToList());
MakeLog("S2.ToArray", test.Select(o =>
{
var sw = new Stopwatch();
GC.Collect();
sw.Start();
var ret = dataS2.ToArray();
sw.Stop();
return sw.ElapsedMilliseconds;
}).ToList());
}
private void TestMain()
{
const int times = 100;
const int count = 1_000_000 + 1;
Test1(times, count);
Test2(times, count);
Test3(times, count);
}
I got these results on my machine:
Group1:
C.ToList 761.79 ms -> [775, 755, 759, 759, 756, 759, 765, 750, 757, 762, 759, 754, 757, 753, 763, 753, 759, 756, 768, 754, 763, 757, 757, 777, 780, 758, 754, 758, 762, 754, 758, 757, 763, 758, 760, 754, 761, 755, 764, 847, 952, 755, 747, 763, 760, 758, 754, 763, 761, 758, 750, 764, 757, 763, 762, 756, 753, 759, 759, 757, 758, 779, 765, 760, 760, 756, 760, 756, 755, 764, 759, 753, 757, 760, 752, 764, 758, 760, 758, 760, 755, 761, 751, 753, 761, 762, 761, 758, 759, 752, 765, 756, 760, 755, 757, 753, 760, 751, 755, 779]
C.ToArray 782.56 ms -> [783, 774, 771, 771, 773, 774, 775, 775, 772, 770, 771, 774, 771, 1023, 975, 772, 767, 776, 771, 779, 772, 779, 775, 771, 775, 773, 775, 771, 765, 774, 770, 781, 772, 771, 781, 762, 817, 770, 775, 779, 769, 774, 763, 775, 777, 769, 777, 772, 775, 778, 775, 771, 770, 774, 772, 769, 772, 769, 774, 775, 768, 775, 769, 774, 771, 776, 774, 773, 778, 769, 778, 767, 770, 787, 783, 779, 771, 768, 805, 780, 779, 767, 773, 771, 773, 785, 1044, 853, 775, 774, 775, 771, 770, 769, 770, 776, 770, 780, 821, 770]
S.ToList 704.2 ms -> [687, 702, 709, 691, 694, 710, 696, 698, 700, 694, 701, 719, 706, 694, 702, 699, 699, 703, 704, 701, 703, 705, 697, 707, 691, 697, 707, 692, 721, 698, 695, 700, 704, 700, 701, 710, 700, 705, 697, 711, 694, 700, 695, 698, 701, 692, 696, 702, 690, 699, 708, 700, 703, 714, 701, 697, 700, 699, 694, 701, 697, 696, 699, 694, 709, 1068, 690, 706, 699, 699, 695, 708, 695, 704, 704, 700, 695, 704, 695, 696, 702, 700, 710, 708, 693, 697, 702, 694, 700, 706, 699, 695, 706, 714, 704, 700, 695, 697, 707, 704]
S.ToArray 742.5 ms -> [742, 743, 733, 745, 741, 724, 738, 745, 728, 732, 740, 727, 739, 740, 726, 744, 758, 732, 744, 745, 730, 739, 738, 723, 745, 757, 729, 741, 736, 724, 744, 756, 739, 766, 737, 725, 741, 742, 736, 748, 742, 721, 746, 1043, 806, 747, 731, 727, 742, 742, 726, 738, 746, 727, 739, 743, 730, 744, 753, 741, 739, 746, 728, 740, 744, 734, 734, 738, 731, 747, 736, 731, 765, 735, 726, 740, 743, 730, 746, 742, 725, 731, 757, 734, 738, 741, 732, 747, 744, 721, 742, 741, 727, 745, 740, 730, 747, 760, 737, 740]
C1.ToList 32.34 ms -> [35, 31, 31, 31, 32, 31, 31, 31, 31, 31, 31, 31, 31, 31, 33, 32, 31, 31, 31, 31, 30, 32, 31, 31, 31, 31, 32, 30, 31, 31, 31, 30, 32, 31, 31, 31, 36, 31, 31, 31, 32, 30, 31, 32, 31, 31, 31, 31, 31, 32, 31, 31, 31, 31, 33, 32, 31, 32, 31, 31, 33, 31, 31, 31, 31, 31, 32, 31, 32, 31, 34, 38, 68, 42, 79, 33, 31, 31, 31, 31, 31, 30, 30, 30, 30, 31, 31, 31, 31, 32, 31, 32, 31, 31, 31, 32, 33, 33, 31, 31]
C1.ToArray 56.32 ms -> [57, 56, 59, 54, 54, 55, 56, 57, 54, 54, 55, 55, 57, 56, 59, 57, 56, 58, 56, 56, 54, 56, 57, 55, 55, 55, 57, 58, 57, 58, 55, 55, 56, 55, 57, 56, 56, 59, 56, 56, 56, 56, 58, 56, 57, 56, 56, 57, 56, 55, 56, 56, 56, 59, 56, 56, 56, 55, 55, 54, 55, 54, 57, 56, 56, 56, 55, 55, 56, 56, 56, 59, 56, 56, 57, 56, 57, 56, 56, 56, 56, 62, 55, 56, 56, 56, 69, 57, 58, 56, 57, 58, 56, 57, 56, 56, 56, 56, 56, 56]
S1.ToList 88.69 ms -> [96, 90, 90, 89, 91, 88, 89, 90, 96, 89, 89, 89, 90, 90, 90, 89, 90, 90, 89, 90, 89, 91, 89, 91, 89, 91, 89, 90, 90, 89, 87, 88, 87, 88, 87, 87, 87, 87, 88, 88, 87, 87, 89, 87, 87, 87, 91, 88, 87, 86, 89, 87, 90, 89, 89, 90, 89, 87, 87, 87, 86, 87, 88, 90, 88, 87, 87, 92, 87, 87, 88, 88, 88, 86, 86, 87, 88, 87, 87, 87, 89, 87, 89, 87, 90, 89, 89, 89, 91, 89, 90, 89, 90, 88, 90, 90, 90, 88, 89, 89]
S1.ToArray 143.26 ms -> [130, 129, 130, 131, 133, 130, 131, 130, 135, 137, 130, 136, 132, 131, 130, 131, 132, 130, 132, 136, 130, 131, 157, 153, 194, 364, 176, 189, 203, 194, 189, 192, 183, 140, 142, 147, 145, 134, 159, 158, 142, 167, 130, 143, 145, 144, 160, 154, 156, 153, 153, 164, 142, 145, 137, 134, 145, 143, 142, 135, 133, 133, 135, 134, 134, 139, 139, 133, 134, 141, 133, 132, 133, 132, 133, 131, 135, 132, 133, 132, 128, 128, 130, 132, 129, 129, 129, 129, 129, 128, 134, 129, 129, 129, 129, 128, 128, 137, 130, 131]
C2.ToList 3.25 ms -> [5, 3, 3, 3, 3, 4, 3, 4, 3, 4, 3, 3, 3, 4, 4, 3, 3, 3, 4, 3, 3, 3, 3, 4, 3, 4, 3, 4, 3, 3, 4, 4, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 3, 4, 3, 3, 3, 3, 3, 4, 3, 4, 3, 3, 3, 4, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 3, 4, 3, 4, 3, 3, 3, 4, 3, 3, 4, 3, 3, 3, 4, 3, 3, 3, 3, 3]
C2.ToArray 3.37 ms -> [4, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 3, 4, 3, 5, 4, 9, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 3, 3, 3, 3, 3, 4, 4, 3, 3, 4, 4, 3, 3, 3, 4, 3, 3, 3, 3, 4, 3, 3, 3, 3, 3, 4, 4, 3, 4, 4, 3, 3, 4, 3, 3, 4, 3, 4, 4, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 3, 3, 4, 3, 3, 3, 3, 3, 4, 4, 3, 3, 3, 3, 3, 4, 3, 4, 3, 3, 3]
S2.ToList 37.72 ms -> [38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 40, 38, 38, 39, 39, 38, 38, 38, 38, 37, 37, 37, 37, 39, 37, 37, 39, 38, 37, 37, 37, 37, 39, 38, 37, 37, 38, 37, 38, 37, 37, 38, 37, 37, 37, 38, 37, 37, 36, 37, 38, 37, 39, 37, 39, 38, 37, 38, 38, 38, 38, 38, 38, 37, 38, 38, 38, 38, 38, 37, 38, 37, 37, 38, 37, 37, 39, 41, 37, 38, 38, 37, 37, 37, 37, 38, 37, 37, 37, 40, 37, 37, 37, 37, 39, 38]
S2.ToArray 38.86 ms -> [39, 37, 39, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 39, 38, 38, 38, 38, 38, 38, 38, 38, 39, 39, 38, 38, 38, 39, 37, 38, 38, 38, 38, 38, 37, 37, 38, 37, 37, 38, 38, 40, 38, 38, 38, 38, 38, 39, 38, 38, 39, 38, 38, 39, 38, 38, 40, 38, 39, 38, 38, 39, 38, 38, 38, 38, 38, 39, 38, 38, 38, 39, 39, 37, 38, 38, 39, 71, 78, 37, 37, 37, 39, 38, 38, 39, 38, 38, 38, 38, 38, 39, 38, 38, 38, 39, 38, 38, 38]
Group2:
C.ToList 756.81 ms
C.ToArray 774.21 ms
S.ToList 709.7 ms
S.ToArray 753.51 ms
C1.ToList 32.06 ms
C1.ToArray 56.58 ms
S1.ToList 89.43 ms
S1.ToArray 132.85 ms
C2.ToList 3.45 ms
C2.ToArray 3.36 ms
S2.ToList 41.43 ms
S2.ToArray 40.84 ms
Group3:
C.ToList 756.64 ms
C.ToArray 771.56 ms
S.ToList 705.42 ms
S.ToArray 749.59 ms
C1.ToList 31.45 ms
C1.ToArray 57.03 ms
S1.ToList 91.26 ms
S1.ToArray 129.77 ms
C2.ToList 3.26 ms
C2.ToArray 3.29 ms
S2.ToList 41.57 ms
S2.ToArray 40.69 ms
Group4:
C.ToList 729.65 ms -> [749, 730, 721, 719, 723, 743, 721, 724, 727, 722, 716, 725, 723, 726, 718, 722, 731, 722, 723, 725, 723, 722, 728, 726, 728, 718, 726, 1088, 788, 737, 729, 710, 730, 728, 717, 723, 728, 721, 722, 728, 722, 736, 723, 729, 732, 724, 726, 727, 728, 728, 726, 726, 725, 727, 725, 728, 728, 718, 724, 725, 726, 724, 726, 729, 727, 722, 722, 725, 725, 728, 724, 727, 738, 717, 726, 723, 725, 725, 727, 724, 720, 726, 726, 723, 727, 730, 723, 721, 725, 727, 727, 733, 720, 722, 722, 725, 722, 725, 728, 726]
C.ToArray 788.36 ms -> [748, 740, 742, 797, 1090, 774, 781, 787, 784, 786, 786, 782, 781, 781, 784, 783, 783, 781, 783, 787, 783, 784, 775, 789, 784, 785, 778, 774, 781, 783, 786, 781, 780, 788, 778, 785, 777, 781, 786, 782, 781, 787, 782, 787, 784, 773, 783, 782, 781, 777, 783, 781, 785, 788, 777, 776, 784, 784, 783, 789, 778, 781, 791, 768, 779, 783, 781, 787, 786, 781, 784, 781, 785, 781, 780, 809, 1155, 780, 790, 789, 783, 776, 785, 783, 786, 787, 782, 782, 787, 777, 779, 784, 783, 776, 786, 775, 782, 779, 784, 784]
S.ToList 705.54 ms -> [690, 705, 709, 708, 702, 707, 703, 696, 703, 702, 700, 703, 700, 707, 705, 699, 697, 703, 695, 698, 707, 697, 711, 710, 699, 700, 708, 707, 693, 710, 704, 691, 702, 700, 703, 700, 705, 700, 703, 695, 709, 705, 698, 699, 709, 700, 699, 704, 691, 705, 703, 700, 708, 1048, 710, 706, 706, 692, 702, 705, 695, 701, 710, 697, 698, 706, 705, 707, 707, 695, 698, 704, 698, 699, 705, 698, 703, 702, 701, 697, 702, 702, 704, 703, 699, 707, 703, 705, 701, 717, 698, 695, 713, 696, 708, 705, 697, 699, 700, 698]
S.ToArray 745.01 ms -> [751, 743, 727, 734, 736, 745, 739, 750, 739, 750, 758, 739, 744, 738, 730, 744, 745, 739, 744, 750, 733, 735, 743, 731, 749, 748, 727, 746, 749, 731, 737, 803, 1059, 756, 769, 748, 740, 745, 741, 746, 749, 732, 741, 742, 732, 744, 746, 737, 742, 739, 733, 744, 741, 729, 746, 760, 725, 741, 764, 739, 750, 751, 727, 745, 738, 727, 735, 741, 720, 736, 740, 733, 741, 746, 731, 749, 756, 740, 738, 736, 732, 741, 741, 733, 741, 744, 736, 742, 742, 735, 743, 746, 729, 748, 765, 743, 734, 742, 728, 749]
C1.ToList 32.27 ms -> [36, 31, 31, 32, 31, 32, 31, 30, 32, 30, 30, 30, 34, 32, 31, 31, 31, 31, 31, 31, 31, 32, 38, 51, 68, 57, 35, 30, 31, 31, 30, 30, 33, 30, 31, 34, 31, 34, 32, 31, 31, 31, 31, 32, 30, 30, 31, 30, 31, 31, 32, 31, 31, 31, 32, 31, 31, 31, 32, 31, 33, 31, 31, 32, 30, 30, 30, 30, 30, 33, 30, 33, 32, 31, 30, 31, 31, 32, 32, 31, 35, 31, 34, 31, 31, 32, 31, 31, 32, 31, 32, 31, 31, 35, 31, 31, 31, 31, 31, 32]
C1.ToArray 56.72 ms -> [58, 56, 57, 57, 59, 58, 58, 57, 56, 59, 57, 55, 55, 54, 56, 55, 56, 56, 57, 59, 56, 55, 58, 56, 55, 55, 55, 55, 58, 58, 55, 57, 57, 56, 57, 57, 57, 57, 59, 59, 56, 57, 56, 57, 57, 56, 57, 59, 58, 56, 57, 57, 57, 58, 56, 56, 59, 56, 59, 57, 57, 57, 57, 59, 57, 56, 57, 56, 58, 56, 57, 56, 57, 59, 55, 58, 55, 55, 56, 56, 56, 56, 56, 56, 56, 56, 56, 57, 56, 56, 57, 56, 56, 57, 58, 57, 57, 57, 57, 57]
S1.ToList 90.72 ms -> [95, 90, 90, 89, 89, 89, 91, 89, 89, 87, 91, 89, 89, 89, 91, 89, 89, 89, 90, 89, 89, 90, 88, 89, 88, 90, 89, 90, 89, 89, 90, 90, 89, 89, 90, 91, 89, 91, 89, 90, 89, 89, 90, 91, 89, 89, 89, 89, 89, 89, 90, 89, 89, 89, 90, 89, 90, 89, 91, 89, 90, 89, 90, 89, 90, 89, 96, 89, 90, 89, 89, 89, 89, 89, 90, 89, 89, 89, 90, 87, 89, 90, 90, 91, 89, 91, 89, 89, 90, 91, 90, 89, 93, 144, 149, 90, 90, 89, 89, 89]
S1.ToArray 131.4 ms -> [130, 128, 127, 134, 129, 129, 130, 136, 131, 130, 132, 132, 133, 131, 132, 131, 133, 132, 130, 131, 132, 131, 130, 133, 133, 130, 130, 131, 131, 131, 132, 134, 131, 131, 132, 131, 132, 131, 134, 131, 131, 130, 131, 131, 130, 132, 129, 131, 131, 131, 132, 131, 133, 134, 131, 131, 132, 132, 131, 133, 131, 131, 130, 133, 131, 130, 134, 132, 131, 132, 132, 131, 131, 134, 131, 131, 132, 132, 131, 130, 138, 130, 130, 131, 132, 132, 130, 134, 131, 131, 132, 131, 130, 132, 133, 131, 131, 131, 130, 131]
C2.ToList 3.21 ms -> [4, 3, 3, 3, 4, 3, 4, 4, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 3, 3, 3, 3, 4, 3, 3, 3, 3, 3, 4, 3, 4, 3, 3, 3, 3, 3, 4, 3, 3, 4, 3, 3, 3, 3, 3, 3, 3, 4, 3, 3, 4, 3, 3, 3, 3, 3, 3, 4, 3, 4, 3, 3, 4, 4, 4, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 3, 3, 3, 4, 4, 3, 3, 3, 3, 3, 4, 3, 3, 3]
C2.ToArray 3.22 ms -> [4, 3, 3, 3, 3, 3, 3, 3, 3, 3, 5, 4, 3, 3, 3, 4, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 3, 3, 3, 3, 3, 3, 4, 3, 4, 3, 3, 3, 4, 3, 4, 3, 3, 3, 4, 4, 3, 3, 3, 3, 3, 3, 3, 3, 4, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 3, 3, 3, 4, 3, 4, 3, 3, 3, 3, 3, 4, 3, 3, 3, 4, 3, 4, 3, 3, 3, 3, 4]
S2.ToList 41.46 ms -> [42, 40, 41, 40, 42, 40, 40, 40, 40, 40, 40, 40, 40, 41, 40, 40, 41, 40, 40, 40, 39, 41, 41, 39, 40, 40, 43, 40, 39, 40, 40, 40, 40, 40, 40, 41, 40, 40, 40, 43, 40, 43, 75, 76, 47, 39, 40, 40, 40, 40, 42, 40, 41, 40, 40, 40, 44, 41, 40, 42, 42, 40, 41, 41, 41, 41, 41, 40, 41, 41, 41, 41, 42, 41, 40, 41, 41, 42, 42, 41, 40, 41, 41, 41, 41, 41, 40, 42, 40, 42, 41, 41, 41, 43, 41, 41, 41, 41, 42, 41]
S2.ToArray 41.14 ms -> [42, 41, 41, 40, 40, 40, 40, 41, 41, 42, 41, 42, 41, 41, 41, 42, 41, 41, 42, 41, 41, 41, 41, 41, 42, 40, 41, 40, 42, 40, 42, 41, 40, 42, 41, 41, 43, 42, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 40, 40, 41, 41, 41, 40, 42, 41, 41, 41, 41, 41, 40, 41, 41, 42, 41, 41, 41, 42, 41, 41, 41, 41, 41, 41, 42, 42, 42, 41, 45, 46, 41, 40, 41, 41, 42, 41, 41, 41, 41, 41, 41, 40, 41, 43, 40, 40, 40, 40, 43, 41]
Group5:
C.ToList 757.06 ms -> [770, 752, 752, 751, 778, 763, 761, 763, 747, 758, 748, 747, 754, 749, 752, 753, 756, 762, 750, 753, 756, 749, 755, 757, 755, 756, 755, 744, 753, 758, 747, 751, 759, 751, 761, 755, 746, 752, 752, 749, 746, 752, 753, 755, 752, 755, 754, 754, 966, 937, 749, 759, 748, 747, 754, 749, 755, 750, 746, 754, 757, 752, 753, 745, 758, 755, 761, 753, 751, 755, 755, 752, 746, 756, 755, 746, 742, 751, 751, 749, 752, 751, 756, 756, 755, 742, 749, 754, 749, 756, 753, 751, 754, 752, 751, 754, 753, 749, 755, 756]
C.ToArray 772.8 ms -> [766, 772, 755, 763, 758, 767, 763, 762, 761, 768, 769, 763, 770, 757, 765, 760, 766, 759, 764, 761, 760, 777, 1102, 881, 759, 765, 758, 762, 772, 761, 758, 757, 765, 769, 769, 761, 762, 762, 763, 760, 770, 764, 760, 768, 758, 766, 763, 770, 769, 761, 764, 761, 761, 767, 761, 762, 764, 757, 765, 766, 767, 771, 753, 762, 769, 768, 759, 764, 764, 760, 763, 763, 763, 763, 763, 767, 761, 771, 760, 765, 760, 758, 768, 770, 751, 771, 767, 771, 765, 763, 760, 765, 765, 769, 767, 767, 1193, 774, 767, 764]
S.ToList 704.73 ms -> [682, 708, 705, 699, 705, 704, 695, 703, 702, 699, 701, 708, 699, 702, 703, 701, 701, 699, 701, 707, 707, 700, 701, 705, 700, 697, 706, 702, 701, 706, 699, 692, 702, 697, 707, 704, 697, 698, 699, 699, 702, 703, 698, 697, 702, 703, 702, 704, 694, 697, 707, 695, 711, 710, 700, 693, 703, 699, 699, 706, 698, 701, 703, 704, 698, 706, 700, 704, 701, 699, 702, 705, 694, 698, 709, 736, 1053, 704, 694, 700, 698, 696, 701, 700, 700, 706, 706, 692, 698, 707, 703, 695, 703, 699, 694, 708, 695, 694, 706, 695]
S.ToArray 744.17 ms -> [746, 740, 725, 740, 739, 731, 746, 760, 735, 738, 740, 734, 744, 748, 737, 744, 745, 727, 736, 738, 728, 743, 745, 735, 748, 760, 739, 748, 762, 742, 741, 747, 733, 746, 758, 742, 742, 741, 724, 744, 747, 727, 740, 740, 729, 742, 757, 741, 740, 742, 726, 739, 746, 1133, 749, 737, 730, 740, 747, 733, 747, 752, 731, 747, 742, 730, 741, 749, 731, 749, 743, 730, 747, 742, 731, 737, 745, 734, 739, 735, 727, 743, 752, 731, 744, 742, 729, 740, 746, 731, 739, 746, 733, 745, 743, 733, 739, 742, 727, 737]
C1.ToList 31.71 ms -> [35, 32, 32, 30, 31, 33, 31, 32, 32, 31, 31, 32, 32, 33, 32, 31, 31, 32, 31, 32, 32, 32, 31, 32, 33, 32, 31, 31, 31, 32, 31, 34, 31, 31, 32, 33, 32, 32, 31, 32, 34, 32, 31, 32, 33, 31, 32, 32, 31, 32, 32, 32, 32, 32, 32, 31, 31, 32, 31, 33, 30, 31, 32, 30, 30, 33, 32, 32, 34, 31, 31, 31, 31, 32, 31, 31, 31, 31, 32, 31, 31, 33, 31, 32, 32, 32, 33, 32, 31, 31, 31, 31, 31, 32, 32, 33, 32, 31, 31, 32]
C1.ToArray 59.53 ms -> [63, 57, 58, 58, 57, 59, 59, 57, 60, 131, 127, 67, 58, 56, 59, 56, 57, 58, 58, 58, 57, 59, 60, 57, 57, 59, 60, 57, 57, 57, 58, 58, 58, 58, 57, 57, 61, 57, 58, 57, 57, 57, 57, 57, 58, 58, 58, 58, 57, 58, 59, 57, 58, 57, 57, 59, 58, 58, 59, 57, 59, 57, 56, 56, 59, 56, 56, 59, 57, 58, 58, 58, 57, 58, 59, 59, 58, 57, 58, 62, 65, 57, 57, 57, 58, 60, 59, 58, 59, 57, 58, 57, 58, 59, 58, 58, 58, 59, 60, 58]
S1.ToList 82.78 ms -> [87, 82, 83, 83, 82, 82, 83, 84, 82, 83, 84, 84, 84, 82, 82, 84, 82, 84, 83, 84, 82, 82, 82, 81, 83, 83, 83, 84, 84, 82, 82, 83, 83, 83, 82, 83, 85, 83, 82, 82, 84, 82, 82, 83, 83, 83, 82, 82, 82, 83, 82, 83, 82, 84, 82, 83, 82, 83, 82, 82, 82, 84, 82, 83, 82, 82, 86, 83, 83, 82, 83, 83, 83, 82, 84, 82, 83, 81, 82, 82, 82, 82, 83, 83, 83, 82, 83, 84, 83, 82, 83, 83, 83, 82, 83, 84, 82, 82, 83, 83]
S1.ToArray 122.3 ms -> [122, 119, 119, 120, 119, 120, 120, 121, 119, 119, 122, 120, 120, 120, 122, 120, 123, 120, 120, 120, 121, 123, 120, 120, 120, 121, 120, 121, 122, 120, 123, 119, 121, 118, 121, 120, 120, 120, 119, 124, 119, 121, 119, 120, 120, 120, 120, 120, 122, 121, 123, 230, 203, 123, 119, 119, 122, 119, 120, 120, 120, 122, 120, 121, 120, 121, 120, 121, 120, 121, 120, 120, 120, 121, 122, 121, 123, 119, 119, 119, 119, 121, 120, 120, 120, 122, 121, 122, 119, 120, 120, 121, 121, 120, 121, 120, 121, 118, 118, 118]
C2.ToList 3.43 ms -> [5, 3, 4, 4, 4, 3, 4, 4, 4, 4, 4, 3, 3, 3, 4, 3, 3, 3, 4, 3, 4, 3, 4, 3, 4, 4, 3, 3, 3, 3, 4, 3, 3, 3, 4, 3, 4, 3, 3, 3, 4, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 3, 3, 6, 4, 4, 3, 3, 4, 3, 3, 4, 3, 3, 3, 3, 3, 3, 3, 4, 3, 3, 3, 3, 3, 3, 4, 3, 4, 4, 4, 3, 4, 4, 3, 4, 4, 4, 4, 4, 4, 3, 3, 3, 4, 4, 3, 3, 3, 3]
C2.ToArray 3.48 ms -> [3, 3, 3, 3, 4, 4, 3, 4, 4, 4, 3, 4, 3, 3, 4, 3, 3, 4, 3, 4, 3, 3, 3, 4, 3, 3, 3, 4, 3, 3, 3, 3, 4, 3, 4, 3, 3, 4, 3, 4, 3, 3, 3, 3, 4, 3, 3, 3, 3, 4, 3, 4, 3, 3, 4, 3, 3, 4, 3, 3, 4, 4, 3, 3, 4, 3, 4, 4, 3, 4, 4, 4, 4, 4, 3, 3, 3, 4, 4, 3, 4, 4, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 3, 4, 4, 4, 4, 3]
S2.ToList 41.47 ms -> [41, 41, 49, 67, 82, 41, 41, 40, 40, 40, 40, 40, 41, 40, 40, 40, 40, 40, 41, 40, 42, 42, 40, 40, 41, 41, 41, 40, 41, 40, 41, 40, 41, 40, 42, 41, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 41, 41, 41, 41, 41, 42, 41, 41, 41, 42, 40, 41, 40, 40, 40, 42, 40, 41, 42, 41, 42, 41, 42, 40, 41, 41, 41, 41, 41, 41, 41, 41, 40, 41, 40, 41, 41, 41, 40, 41, 41, 40, 40, 41, 41, 41, 41, 41, 43, 40, 40, 41, 42, 41]
S2.ToArray 40.62 ms -> [42, 41, 44, 40, 40, 40, 40, 41, 41, 40, 41, 41, 41, 40, 41, 41, 40, 41, 41, 40, 41, 40, 40, 41, 42, 41, 41, 41, 40, 40, 40, 40, 40, 41, 41, 42, 40, 41, 41, 41, 41, 41, 40, 42, 40, 40, 41, 41, 41, 40, 41, 40, 40, 40, 40, 40, 41, 40, 40, 41, 40, 40, 40, 40, 41, 40, 41, 41, 41, 40, 41, 41, 40, 41, 40, 41, 42, 40, 41, 41, 42, 41, 41, 40, 41, 40, 41, 40, 41, 41, 40, 40, 40, 41, 41, 40, 40, 40, 40, 40]
Due to stackoverflow's limit to the characters amount of the answer, the sample lists of Group2 and Group3 are omitted.
As you can see, it's really not important to use ToList or ToArry in most cases.
While processing runtime-calculated IEnumerable<T> objects, if the load brought by calculation is heavy than memory allocation and copy operations of ToList and ToArray, the disparity is insignificant (C.ToList vs C.ToArray and S.ToList vs S.ToArray).
The difference can be observed only on non-runtime-calculated IEnumerable<T> only objects (C1.ToList vs C1.ToArray and S1.ToList vs S1.ToArray). But the absolute difference (<60ms) is still acceptable on an one million small object IEnumerable<T>. In fact, the difference is decided by the implementation of Enumerator<T> of IEnumerable<T>. So, if your program is really really really sensitive on this, you do have to profile, profile, profile! At last you'll probably find that the bottleneck is not on ToList or ToArray, but the detail of enumerators.
And, the result of C2.ToList vs C2.ToArray and S2.ToList vs S2.ToArray shows that, you really don't need to care ToList or ToArray on non-runtime-calculated ICollection<T> objects.
Of course, this is just results on my machine, the actual time spend of these operations on different machine will not be the same, you can find out on your machine using code above.
The only reason you need to make a choice is that, you have specific needs on List<T> or T[], as described by the answer of @Jeppe Stig Nielsen.
