How do I clone a generic list in C#?

Question

I have a generic list of objects in C#, and wish to clone the list. The items within the list are cloneable, but there doesn\'t seem to be an option to do list.Clone()

Answer 1

If your elements are value types, then you can just do:

List newList = new List(oldList);

However, if they are reference types and you want a deep copy (assuming your elements properly implement ICloneable), you could do something like this:

List oldList = new List();
List newList = new List(oldList.Count);

oldList.ForEach((item) =>
    {
        newList.Add((ICloneable)item.Clone());
    });

Obviously, replace ICloneable in the above generics and cast with whatever your element type is that implements ICloneable.

If your element type doesn't support ICloneable but does have a copy-constructor, you could do this instead:

List oldList = new List();
List newList = new List(oldList.Count);

oldList.ForEach((item)=>
    {
        newList.Add(new YourType(item));
    });

Personally, I would avoid ICloneable because of the need to guarantee a deep copy of all members. Instead, I'd suggest the copy-constructor or a factory method like YourType.CopyFrom(YourType itemToCopy) that returns a new instance of YourType.

Any of these options could be wrapped by a method (extension or otherwise).