CODEWITHSUNDEEP
c#ooplistforeachcopy
ratty
ratty

Reputation: 13434

How do I copy items from list to list without foreach?

How do I transfer the items contained in one List to another in C# without using foreach?

Upvotes: 381

Views: 574733

Answers (10)

Daniel Möller
Daniel Möller

Reputation: 86600

Adding to the top answers, if you want copies of "the objects in the list", then you can use Select and make the copies. (While the other answers make "a copy of a list", this answer makes "a list of copies").

Suppose your item has a Copy method:

List<MyObject> newList = oldList.Select(item => item.Copy()).ToList();

Or that you can create a new object from the previous one with a constructor:

List<MyObject> newList = oldList.Select(item => new MyObject(item)).ToList();

The result of Select is an IEnumerable<MyObject> that you can also pass to AddRange for instance, if your goal is to add to an existing list.

Upvotes: 2

Jon Skeet
Jon Skeet

Reputation: 1499760

To add the contents of one list to another list which already exists, you can use:

targetList.AddRange(sourceList);

If you're just wanting to create a new copy of the list, see the top answer.

Upvotes: 211

Lasse V. Karlsen
Lasse V. Karlsen

Reputation: 391286

You could try this:

List<Int32> copy = new List<Int32>(original);

or if you're using C# 3 and .NET 3.5, with Linq, you can do this:

List<Int32> copy = original.ToList();

I see that this answer is still getting upvotes. Well, here's a secret for ya: the above answer is still using a foreach. Please don't upvote this any further.

Upvotes: 672

Black Dream
Black Dream

Reputation: 21

public static List<string> GetClone(this List<string> source)
{
    return source.Select(item => (string)item.Clone()).ToList();
}

Upvotes: 1

Rajeev
Rajeev

Reputation: 405

Easy to map different set of list by linq without for loop

var List1= new List<Entities1>();

var List2= new List<Entities2>();

var List2 = List1.Select(p => new Entities2
        {
            EntityCode = p.EntityCode,
            EntityId = p.EntityId,
            EntityName = p.EntityName
        }).ToList();

Upvotes: 4

Paras
Paras

Reputation: 3067

For a list of elements

List<string> lstTest = new List<string>();

lstTest.Add("test1");
lstTest.Add("test2");
lstTest.Add("test3");
lstTest.Add("test4");
lstTest.Add("test5");
lstTest.Add("test6");

If you want to copy all the elements

List<string> lstNew = new List<string>();
lstNew.AddRange(lstTest);

If you want to copy the first 3 elements 

List<string> lstNew = lstTest.GetRange(0, 3);

Upvotes: 46

Jim Stevens
Jim Stevens

Reputation: 1

OK this is working well From the suggestions above GetRange( ) does not work for me with a list as an argument...so sweetening things up a bit from posts above: ( thanks everyone :)

/*  Where __strBuf is a string list used as a dumping ground for data  */
public List < string > pullStrLst( )
{
    List < string > lst;

    lst = __strBuf.GetRange( 0, __strBuf.Count );     

    __strBuf.Clear( );

    return( lst );
}

Upvotes: -1

usefulBee
usefulBee

Reputation: 9692

And this is if copying a single property to another list is needed:

targetList.AddRange(sourceList.Select(i => i.NeededProperty));

Upvotes: 7

Web Developer India
Web Developer India

Reputation: 677

This method will create a copy of your list but your type should be serializable.

Use: 

List<Student> lstStudent = db.Students.Where(s => s.DOB < DateTime.Now).ToList().CopyList();

Method:

public static List<T> CopyList<T>(this List<T> lst)
    {
        List<T> lstCopy = new List<T>();
        foreach (var item in lst)
        {
            using (MemoryStream stream = new MemoryStream())
            {
                BinaryFormatter formatter = new BinaryFormatter();
                formatter.Serialize(stream, item);
                stream.Position = 0;
                lstCopy.Add((T)formatter.Deserialize(stream));
            }
        }
        return lstCopy;
    }

Upvotes: 4

ratty
ratty

Reputation: 13434

Here another method but it is little worse compare to other.

List<int> i=original.Take(original.count).ToList();

Upvotes: -9

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