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I know this Questions is asked and has answer already here: C# how to assign List<T> without being a reference?

but as @Dev said it is still being referenced. my "name_list1" is static and then I am coping like:

name_list2 = new List<string>(name_list1);

as answered in above link. i have tried all possible solution founded from stackoverflow like: using - AddRange, ToList , ToArray and all. but still it is creating ref only to name_list1. as I am changing object value in name_list2 it is affected in name_list1 too.

I needed to ask this Question again as I am not able to comment on others question due to <50 reputation :P :(

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aru
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  • Could you provide us with complete test code. Something else is happening here since the answer given in the above link does indeed work. Does your list contain value types or reference types? In latter case, changes in the reference objects do affect in both lists. But, for example, adding an object to list2 does not add objects to list1. – Joonas Koski Jan 13 '15 at 05:31
  • i have downloaded "http://www.codeproject.com/Articles/17424/CNC-Graphical-Backplotter?msg=4959363#xx4959363xx" just for understanding c#. in this source project it has "CSharpBasicViewerControl" which has "MG_CS_BasicViewer" user control. which has "MotionBlocks" list. in "CSharpBasicViewerApp" it has "frmViewer" form. in it they are using MotionBlocks" list. i just tried to do like: public static List motionBlocks; motionBlocks = new List(MG_CS_BasicViewer.MotionBlocks); then motionBlocks[2].Xpos = 100; so the actual MotionBlocks[2]'s Xpos is also changed. – aru Jan 13 '15 at 06:08
  • how can i find that whether the object of list is reference object or not? – aru Jan 13 '15 at 06:21
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    http://msdn.microsoft.com/en-us/library/4d43ts61(v=vs.90).aspx So basicly all objects are reference types and built-in types (int, double, etc.) and structures are value types. – Joonas Koski Jan 13 '15 at 06:41

2 Answers2

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You need to iterate through first list, and clone all the objects, and then add these to list2.

Otherwise, even though list object are different, the items they refer to are still same so any change made to list items, will be reflected through other list.

Refer to this SO answer for how to clone. Deep cloning objects.

Also, One concept to understand is that, when you create another list and use AddRange, both list objects are different.
Changes to one list are not reflected in other list. These changes include adding list item, removing list item, ordering list item.
These collection level changes are different from changes in individual list items, which are reflected as individual list items are still the same in both list (unless they are cloned prior to adding to the list).

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Tilak
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To Simply solve this I have added each value of object item manually. As i also tried to iterate through each object to add it in list, and that's didn't work. So For me Simple solution is to write constructor of list item object, which has one argument which accept object type of itself and add all value manually. I will do more on some time to solve this in better way. Thanks all for help :)

And Also we can use: 

public static T DeepCopy<T>(T item)
        {
            BinaryFormatter formatter = new BinaryFormatter();
            MemoryStream stream = new MemoryStream();
            formatter.Serialize(stream, item);
            stream.Seek(0, SeekOrigin.Begin);
            T result = (T)formatter.Deserialize(stream);
            stream.Close();
            return result;
        }
aru
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