Deep copy of objects in C#

Hakger

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18 Jul 2009CPOL

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How to do a deep copy of objects using System.Reflection.

Download source code - 100 KB

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:

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

Hakger

Software Developer (Senior)

Poland

This member has not yet provided a Biography. Assume it's interesting and varied, and probably something to do with programming.

<Runtime.CompilerServices.Extension()> Public Function DeepCopy(Of T)(ByVal obj As T) As T If obj Is Nothing Then Return Nothing Return DirectCast(DeepCopy(obj, New Dictionary(Of Object, Object)()), T) End Function Private Function DeepCopy(ByVal obj As Object, ByVal circular As Dictionary(Of Object, Object)) As Object If obj Is Nothing Then Return Nothing End If Dim typ As Type = obj.GetType() If typ.IsPrimitive OrElse typ Is GetType(String) OrElse typ Is GetType(Decimal) Then Return obj End If If circular.ContainsKey(obj) Then Return circular(obj) End If If typ.IsArray Then Dim typeNoArray As String = typ.FullName.Replace("[]", String.Empty) Dim elementType As Type = Type.GetType(typeNoArray & ", " & typ.Assembly.FullName) Dim arr As Array = obj Dim copied As Array = System.Array.CreateInstance(elementType, arr.Length) circular(obj) = copied For i As Integer = 0 To arr.Length - 1 Dim element As Object = arr.GetValue(i) Dim copy As Object = Nothing If element IsNot Nothing AndAlso circular.ContainsKey(element) Then copy = circular(element) Else copy = DeepCopy(element, circular) End If copied.SetValue(copy, i) Next Return copied 'Convert.ChangeType(copied, obj.GetType()) ElseIf typ.IsClass Then 'class Dim newobj As Object = Activator.CreateInstance(obj.GetType()) circular(obj) = newobj Dim fields As Reflection.FieldInfo() = typ.GetFields(Reflection.BindingFlags.Public Or Reflection.BindingFlags.NonPublic Or Reflection.BindingFlags.Instance) For Each field As Reflection.FieldInfo In fields Dim fieldValue As Object = field.GetValue(obj) If fieldValue Is Nothing Then Continue For End If Dim copy As Object = Nothing If circular.ContainsKey(fieldValue) Then copy = circular(fieldValue) Else copy = DeepCopy(fieldValue, circular) End If field.SetValue(newobj, copy) Next Return newobj ElseIf typ.IsValueType Then 'structure Dim newobj As System.ValueType = Activator.CreateInstance(obj.GetType()) circular(obj) = newobj Dim fields As Reflection.FieldInfo() = typ.GetFields(Reflection.BindingFlags.Public Or Reflection.BindingFlags.NonPublic Or Reflection.BindingFlags.Instance) For Each field As Reflection.FieldInfo In fields Dim fieldValue As Object = field.GetValue(obj) If fieldValue Is Nothing Then Continue For End If Dim copy As Object = Nothing If circular.ContainsKey(fieldValue) Then copy = circular(fieldValue) Else copy = DeepCopy(fieldValue, circular) End If field.SetValue(newobj, copy) Next Return newobj Else Return Nothing End If End Function

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