Conversion of System.Array to List

Question

Last night I had dream that the following was impossible. But in the same dream, someone from SO told me otherwise. Hence I would like to know if it it possible to convert System.Array to List

Array ints = Array.CreateInstance(typeof(int), 5);
ints.SetValue(10, 0);
ints.SetValue(20, 1);
ints.SetValue(10, 2);
ints.SetValue(34, 3);
ints.SetValue(113, 4);

to

List<int> lst = ints.OfType<int>(); // not working

Below link show how it does in c# http://www.codegateway.com/2011/12/c-convert-array-to-list-and-list-to.html — , Feb 29 '12 at 17:00
You have to cast the `Array` to what it actually is, an `int[]`, then you can use `ToList`: `((int[])ints).ToList();` — Tim Schmelter, Dec 04 '15 at 16:39
@naserasadi please consider accepting the answer by Tim Schmelter as this is appears to be the correct answer to your question and even 12 years later this question is showing at the top of search results. Thanks! — David, Feb 26 '22 at 18:30
Why to use System.Array at the first place? I think that need for using System.Array has died out long time ago. Just use typed arrays like int[] or IMyType[], or Lists... You will never have these type of problems. — A. Dzebo, Mar 25 '22 at 09:43
@puzzl that's fine. Just convert it to a list using i.e. LINQ like this: List data = Enum.GetValues(typeof(Days)).OfType().Select(o => o).ToList(); and work with the list. — A. Dzebo, Jan 09 '23 at 14:57

score 509 · Accepted Answer · edited Jan 25 '18 at 02:51

509

Save yourself some pain...

using System.Linq;

int[] ints = new [] { 10, 20, 10, 34, 113 };

List<int> lst = ints.OfType<int>().ToList(); // this isn't going to be fast.

Can also just...

List<int> lst = new List<int> { 10, 20, 10, 34, 113 };

or...

List<int> lst = new List<int>();
lst.Add(10);
lst.Add(20);
lst.Add(10);
lst.Add(34);
lst.Add(113);

or...

List<int> lst = new List<int>(new int[] { 10, 20, 10, 34, 113 });

or...

var lst = new List<int>();
lst.AddRange(new int[] { 10, 20, 10, 34, 113 });

edited Jan 25 '18 at 02:51

Ivan Castellanos

8,041
1
47
42

answered Oct 21 '09 at 19:50

David

19,389
12
63
87

17

Note for completeness: the 2nd method is only available in C# 3.0+. – Jon Seigel Oct 21 '09 at 20:17
25

Since the int array already implements `IEnumerable`, the `OfType()` is not required. `ints.ToList();` suffices. – Heinzi Feb 29 '12 at 17:06
16

For OfType, you need System.Linq – JasonPlutext Jul 27 '12 at 03:18
I tried this and it slowed my program down immensly compared to just putting it manually in a list with a for loop – kenny Mar 15 '14 at 17:58
2

@kenny made some tweaks, the first method here, is definitely not the quickest way to do this. – David Mar 17 '14 at 14:50
18

None of these examples actually answer the actual question. But I guess he accepted the answer so he was happy. Still, not one of these actually convert an Array to a List. "Conversion of System.Array to List". Should add that example for completeness IMO. (Being top answer and all) – Søren Ullidtz Jan 22 '15 at 08:14
@SørenUllidtz The first example does exactly that. – David Jan 22 '15 at 16:12
2

@Dave It's true that OfType will work for the Array class, it's just not using the Array class in the example. And judging by the second comment I'm not the only one who got confused about that. – Søren Ullidtz Jan 26 '15 at 04:07
System.Linq in .Net 4.0 is in System.Core: http://stackoverflow.com/questions/2893601/where-is-system-linq-in-net-4-0 – Chris Feb 18 '16 at 15:15
4

Doesn't answer the question. – Sophie Coyne Mar 30 '16 at 11:51
8

Enum.GetValues(typeof(Enumtype)).Cast().ToList() – Phan Đức Bình Jan 05 '17 at 04:41
1

You can create the list by given array List list = new List(array); – Ghoster Jul 30 '19 at 08:02
Why does this not answer the question? – pete Jun 05 '22 at 23:10
Why did so many people up vote this when it does not answer to question that was asked? – Los2000 Aug 30 '23 at 19:59

Matthew Whited · Answer 2 · 2009-10-21T20:10:50.010

106

There is also a constructor overload for List that will work... But I guess this would required a strong typed array.

//public List(IEnumerable<T> collection)
var intArray = new[] { 1, 2, 3, 4, 5 };
var list = new List<int>(intArray);

... for Array class

var intArray = Array.CreateInstance(typeof(int), 5);
for (int i = 0; i < 5; i++)
    intArray.SetValue(i, i);
var list = new List<int>((int[])intArray);

edited Oct 21 '09 at 20:10

answered Oct 21 '09 at 20:05

Matthew Whited

22,160
4
52
69

Between this approach and the one using `ToList()`, which is more efficient? Or is there a difference? – Ben Sutton Jul 04 '12 at 04:27
1

Hard to say without knowing the real dataset size (List internally uses arrays that must be able to expand. Arrays are immutable.) If you know the List size upfront this way could improve performance slightly… but the gain is going to be so small you may as well use the version you prefer to maintain. – Matthew Whited Jul 05 '12 at 12:32
3

Have you noticed this thread is 6 years old? (And my second answer directly handles his example of using `Array` instead of `int[]`.) – Matthew Whited Dec 04 '15 at 16:40

Tim Schmelter · Answer 3 · 2016-08-28T21:52:55.127

102

Interestingly no one answers the question, OP isn't using a strongly typed int[] but an Array.

You have to cast the Array to what it actually is, an int[], then you can use ToList:

List<int> intList = ((int[])ints).ToList();

Note that Enumerable.ToList calls the list constructor that first checks if the argument can be casted to ICollection<T>(which an array implements), then it will use the more efficient ICollection<T>.CopyTo method instead of enumerating the sequence.

edited Aug 28 '16 at 21:52

answered Dec 04 '15 at 16:40

Tim Schmelter

450,073
74
686
939

21

Thank you, `Enum.GetValues` returns an Array and this helped me out making a list out of it. – Martin Braun Aug 28 '16 at 20:57
4

I know this is old but you are right, the question is answer by this. In my situation a dynamic deserializer returns a system array because it has to be prepared to accept any kind of data type so you can't preload the list until runtime. Thank you – Frank Cedeno May 02 '17 at 14:21

score 27 · Answer 4 · edited Nov 24 '14 at 18:56

27

The simplest method is:

int[] ints = new [] { 10, 20, 10, 34, 113 };

List<int> lst = ints.ToList();

or

List<int> lst = new List<int>();
lst.AddRange(ints);

edited Nov 24 '14 at 18:56

Adam Parkin

17,891
17
66
87

answered Feb 04 '13 at 07:01

Danny

271
3
2

7

One needs `using System.Linq;` for `ToList()` to work. – Jarekczek Jan 07 '18 at 14:41
2

This doesn't work for `Array`. You need to cast it or call `.Cast<>` first. – BlueRaja - Danny Pflughoeft Jun 21 '20 at 21:49
1

have you tested this? – David Feb 26 '22 at 18:34

score 15 · Answer 5 · answered Apr 05 '16 at 09:06

In the case you want to return an array of enums as a list you can do the following.

using System.Linq;

public List<DayOfWeek> DaysOfWeek
{
  get
  {
    return Enum.GetValues(typeof(DayOfWeek))
               .OfType<DayOfWeek>()
               .ToList();
  }
}

score 6 · Answer 6 · answered Jul 18 '17 at 08:58

6

You can do like this basically:

int[] ints = new[] { 10, 20, 10, 34, 113 };

this is your array, and than you can call your new list like this:

 var newList = new List<int>(ints);

You can do this for complex object too.

answered Jul 18 '17 at 08:58

nzrytmn

6,193
1
41
38

Smith · Answer 7 · 2012-03-02T22:30:16.670

5

in vb.net just do this

mylist.addrange(intsArray)

or

Dim mylist As New List(Of Integer)(intsArray)

edited Mar 02 '12 at 22:30

answered May 22 '11 at 12:23

Smith

5,765
17
102
161

2

much better than using OfType<> (my VS2010 would not accept anything OfType...) – scrat.squirrel Apr 18 '12 at 20:55

score 3 · Answer 8 · answered Dec 08 '14 at 01:55

You can just give it try to your code:

Array ints = Array.CreateInstance(typeof(int), 5);
ints.SetValue(10, 0);

ints.SetValue(20, 1);
ints.SetValue(10, 2);
ints.SetValue(34, 3);
ints.SetValue(113, 4);

int[] anyVariable=(int[])ints;

Then you can just use the anyVariable as your code.

score 3 · Answer 9 · answered Jan 01 '21 at 06:56

3

I know two methods:

List<int> myList1 = new List<int>(myArray);

Or,

List<int> myList2 = myArray.ToList();

I'm assuming you know about data types and will change the types as you please.

answered Jan 01 '21 at 06:56

Ashish Neupane

193
2
17

1

This appears to be just a repeat of the existing answers. – Pang Jan 01 '21 at 08:04

score 2 · Answer 10 · answered May 18 '17 at 10:27

2

Just use the existing method.. .ToList();

   List<int> listArray = array.ToList();

KISS(KEEP IT SIMPLE SIR)

answered May 18 '17 at 10:27

Drew Aguirre

375
2
15

score 0 · Answer 11 · answered May 24 '16 at 09:41

I hope this is helpful.

enum TESTENUM
    {
        T1 = 0,
        T2 = 1,
        T3 = 2,
        T4 = 3
    }

get string value

string enumValueString = "T1";

        List<string> stringValueList =  typeof(TESTENUM).GetEnumValues().Cast<object>().Select(m => 
            Convert.ToString(m)
            ).ToList();

        if(!stringValueList.Exists(m => m == enumValueString))
        {
            throw new Exception("cannot find type");
        }

        TESTENUM testEnumValueConvertString;
        Enum.TryParse<TESTENUM>(enumValueString, out testEnumValueConvertString);

get integer value

        int enumValueInt = 1;

        List<int> enumValueIntList =  typeof(TESTENUM).GetEnumValues().Cast<object>().Select(m =>
            Convert.ToInt32(m)
            ).ToList();

        if(!enumValueIntList.Exists(m => m == enumValueInt))
        {
            throw new Exception("cannot find type");
        }

        TESTENUM testEnumValueConvertInt;
        Enum.TryParse<TESTENUM>(enumValueString, out testEnumValueConvertInt);

Conversion of System.Array to List

11 Answers11

Linked

Related