Shallow copying a list with downcasting

Question

I have the class herichary as follows

CEntity---->CNode--->CElement

I have a

class Nodes : List<Cnode>

and

Class Elements : List<Element>

Node class contain common item common across different project Element class has item specific to a project.

I have to shallow copy the element list into the node list (basically down casting the elements to nodes)

Answer 1

Supposing you are using .net 3.0 or greater, the following code creates a NEW list with the SAME elements downcasted to CNodes:

List<CNode> shallowCopyNodesList =  elements.Cast<CNode>().ToList();

Then (if not already present) you should create a constructor taking a List<CNode> in Nodes class and do:

var shallowCopyNodes = new Nodes(shallowCopyNodesList);

Answer 2

You could just do this:

List<CNode> nodes = new List<CNode>();
foreach (CElement element in elements) {
  nodes.Add(element);
}

Where elements is a List.

You don't need to worry about casting back to CNode, because CElement inherits from that. The important thing to note is that the elements in the nodes list (in the example above), are in fact instances of CElement. If you wanted CNode you'd probably have to create a new instance of CNode using a copy constructor:

public CNode(CNode instance)
{
  this.Property = instance.Property;
}

And add a new instance of CNode:

nodes.Add(new CNode(element));

Answer 3

You can use the Cast operator in LINQ.

var nodelist = elementList.Cast<CNode>()
                   .ToList();

Answer 4

What I have done is

nodes.addrange(ElementList.ConvertAll(new Converter<Elements, CNode>(ConvertElementsToNode))));

and

public static CNode ConvertElementsToNode(Element ele)
    {
      return ((CNode) ele);
    } // ConvertElementsToNode

but will there be any performance/ memory issue in this approach.