Click here to Skip to main content
15,868,053 members
Articles / Programming Languages / C#

Deep copy of objects in C#

Rate me:
Please Sign up or sign in to vote.
4.83/5 (15 votes)
18 Jul 2009CPOL 153.3K   1.2K   34   24
How to do a deep copy of objects using System.Reflection.

Introduction

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...)

Background

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:

C#
using System;
using System.Reflection;

namespace HAKGERSoft {

    public class HCloner {

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

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

    }
}

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

History

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).

License

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


Written By
Software Developer (Senior)
Poland Poland
This member has not yet provided a Biography. Assume it's interesting and varied, and probably something to do with programming.

Comments and Discussions

 
BugShould also deep copy valuetypes Pin
jpmik23-Sep-22 2:22
jpmik23-Sep-22 2:22 
QuestionYou have rocked in the first article itself. Thank you for your great contribution. Pin
Ashok Login4-Mar-20 19:55
Ashok Login4-Mar-20 19:55 
SuggestionThis change will make parameterless contructors work Pin
Sakkers23-Apr-19 0:27
Sakkers23-Apr-19 0:27 
It also works on classes without a paramaterless constructor if you switch:
Activator.CreateInstance(obj.GetType());

with
object newObj;
if (type.GetConstructor(Type.EmptyTypes) != null)//does it have a parameterless constructor?
    newObj = Activator.CreateInstance(type);//uses the parameterless contructor
else
    newObj = FormatterServices.GetUninitializedObject(type);//we use this if no parameterless constructor exists


(also switched "obj.GetType()" with "type" since we already have the value in a variable)
Questionobject[,] Array.Copy Pin
nhatnguyen12345678921-May-16 6:15
nhatnguyen12345678921-May-16 6:15 
AnswerRe: object[,] Array.Copy Pin
Member 132772109-Jul-17 2:43
Member 132772109-Jul-17 2:43 
QuestionLooks awesome, bug Throws Exception on System Object Pin
Member 122935161-Feb-16 21:40
Member 122935161-Feb-16 21:40 
SuggestionClasses from different assemblies Pin
Defor64-Sep-13 0:26
Defor64-Sep-13 0:26 
GeneralMy vote of 1 Pin
Aydin Homay15-May-13 1:21
Aydin Homay15-May-13 1:21 
GeneralRe: My vote of 1 Pin
onefootswill28-Jun-14 18:17
onefootswill28-Jun-14 18:17 
GeneralRe: My vote of 1 Pin
Octopod25-Jan-18 6:04
Octopod25-Jan-18 6:04 
QuestionError at "return Convert.ChangeType(copied,obj.GetType() ); " Pin
VigneshPT24-Oct-11 10:36
VigneshPT24-Oct-11 10:36 
QuestionDoesn't work with inheritance Pin
Sean Wolf16-Sep-11 11:46
Sean Wolf16-Sep-11 11:46 
GeneralNow it works with structures! [modified] Pin
Brian Coverstone27-Apr-11 15:59
Brian Coverstone27-Apr-11 15:59 
GeneralExcellent! Pin
flippydeflippydebop1-Aug-09 23:35
flippydeflippydebop1-Aug-09 23:35 
GeneralCircular references. Pin
Andre Luiz Alves Moraes20-Jul-09 3:05
Andre Luiz Alves Moraes20-Jul-09 3:05 
GeneralRe: Circular references. Pin
Hakger22-Jul-09 6:36
Hakger22-Jul-09 6:36 
GeneralRe: Circular references. Pin
Rafi Ben Avi12-Feb-18 20:13
Rafi Ben Avi12-Feb-18 20:13 
GeneralRe: Circular references -> I Found a bug, please add this code Pin
Rafi Ben Avi19-Feb-18 23:22
Rafi Ben Avi19-Feb-18 23:22 
GeneralHi, think of this..... Pin
Binkle@JAM20-Jul-09 1:20
Binkle@JAM20-Jul-09 1:20 
GeneralRe: Hi, think of this..... Pin
Hakger22-Jul-09 6:37
Hakger22-Jul-09 6:37 
GeneralRe: Hi, think of this..... Pin
akshayswaroop18-Nov-09 2:12
akshayswaroop18-Nov-09 2:12 
General[My vote of 2] more clarification Pin
Md. Marufuzzaman18-Jul-09 22:44
professionalMd. Marufuzzaman18-Jul-09 22:44 
GeneralLooks good Pin
The_Mega_ZZTer18-Jul-09 16:27
The_Mega_ZZTer18-Jul-09 16:27 
Generalgj Pin
QuaQua18-Jul-09 15:50
QuaQua18-Jul-09 15:50 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Praise Praise    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.