How to Deep Copy in C#

This tutorial will introduce the method to create a deep copy of a class object in C#.

Deep Copy Object With the BinaryFormatter Class in C#

Deep copy means copying every field of an object to another object, while shallow copy means creating a new class instance and pointing it to the previous class instance’s values. We can use the BinaryFormatter to create a deep copy of a class object in C#. The BinaryFormatter class reads and writes class objects to a stream in binary format. We can use the BinaryFormatter.Serialize() method to write our class object to a memory stream in C#. We can then write the same memory stream to an object with the BinaryFormatter.Deserialize() method and return it. We need to first mark our class with [Serializable] for this approach to work. The following code example shows us how to create a deep copy of an object with the BinaryFormatter class in C#.

using System;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;

namespace deep_copy {
  [Serializable]
  public class Sample {
    public string sampleName { get; set; }
  }
  static class ext {
    public static Sample deepCopy<Sample>(this Sample obj) {
      using (var memStream = new MemoryStream()) {
        var bFormatter = new BinaryFormatter();
        bFormatter.Serialize(memStream, obj);
        memStream.Position = 0;

        return (Sample)bFormatter.Deserialize(memStream);
      }
    }
  }
  class Program {
    static void Main(string[] args) {
      Sample s1 = new Sample();
      s1.sampleName = "Sample number 1";
      Sample s2 = s1.deepCopy();
      Console.WriteLine("Sample 1 = {0}", s1.sampleName);
      Console.WriteLine("Sample 2 = {0}", s2.sampleName);
    }
  }
}

Output:

Sample 1 = Sample number 1
Sample 2 = Sample number 1

In the above code, we created a deep copy of the object s1 of the class Sample and saved it in the object s2 of the same class by using the BinarySerializer class in C#.