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Deep copy of objects in C#

, 18 Jul 2009 CPOL
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How to do a deep copy of objects using System.Reflection.


Below you can find a short article on how to do a deep copy of objects using Reflection in C#. Please be aware that this is my first article here (even first article in the English language...)


The class (called HCloner) has a DeepCopy function. It drills down the entire object fields structure (using System.Reflection) and copies it into a new location that is returned after that.

Members that are copied are fields - no need to copy properties since behind every property, there is a field. A property itself cannot hold any value.

Using the code

Let's look at the "core" code:

using System;
using System.Reflection;

namespace HAKGERSoft {

    public class HCloner {

        public static T DeepCopy<T>(T obj) {
                throw new ArgumentNullException("Object cannot be null");
            return (T)Process(obj);

        static object Process(object obj) {
                return null;
            Type type=obj.GetType();
            if(type.IsValueType || type==typeof(string)) {
                return obj;
            else if(type.IsArray) {
                Type elementType=Type.GetType(
                var array=obj as Array;
                Array copied=Array.CreateInstance(elementType,array.Length);
                for(int i=0; i<array.Length; i++) {
                return Convert.ChangeType(copied,obj.GetType());
            else if(type.IsClass) {
                object toret=Activator.CreateInstance(obj.GetType());
                FieldInfo[] fields=type.GetFields(BindingFlags.Public| 
                foreach(FieldInfo field in fields) {
                    object fieldValue=field.GetValue(obj);
                return toret;
                throw new ArgumentException("Unknown type");


Using it is very simple - just call the DeepCopy function.


This is a very alpha-pre version of my function. I'm looking forward for some feedback from you - any issues found will be analysed and fixed (at least, I'll try).


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Software Developer (Senior)
Poland Poland
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Comments and Discussions

GeneralCircular references. Pin
Andre Luiz Alves Moraes20-Jul-09 4:05
memberAndre Luiz Alves Moraes20-Jul-09 4:05 

I Already done some code like yours and one of the important things to handle is Circular References.

For example if you have a tree class like this:

public class Tree
  public TreeNode _root;

public class TreeNode
  public TreeNode _parent;
  public TreeNode _lChild;
  public TreeNode _rChild;

  public TreeNode(TreeNode parent)
    _parent = parent;

When you call the method to a object of Tree your code will start do copy the nodes of the tree.

The big problem is that de root node of a tree is the parent of some child, so, when you start to copy the child of the root, your code will look into _parent field and will try to copy the root node again. And this cycle will continue until a stack overflow.

To solve that problem i used a collection of cloned objects. It was something like this;

public class CloneList
  private IList _originals;
  private IList _clones;

  public CloneList()
    _originals = new ArrayList();
    _clones = new ArrayList();
  public object getCloneForOriginal(object original)
    if (_originals.Contains(original))
        return _clones[_originals.IndexOf(original)];
      return null;

Thumbs Up | :thumbsup:
GeneralRe: Circular references. Pin
DetoX8322-Jul-09 7:36
memberDetoX8322-Jul-09 7:36 

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