Create a deep copy of a List in C#

This post will discuss how to create a deep copy of a List in C#.

1. Using Constructor

You can use a constructor to create a copy of objects in C#. To create a deep copy of a list of objects, you can iterate through the list and create a copy of each item by invoking its constructor. This approach is can be used if the class is not complex and contains few properties. A typical implementation of this approach would look like below using the Select() or ConvertAll() method:

using System;

using System.Linq;

using System.Collections.Generic;

class Student

{

public string name { get; set; }

public decimal age { get; set; }

public override string ToString() {

return "[" + name + ", " + age + "]";

}

public class Example

{

public static void Main()

{

var list = new List<Student> {

new Student{name = "Olivia", age = 10},

new Student{name = "Robert", age = 20},

new Student{name = "John", age = 15}

};

// Using Select()

var copy1 = list.Select(s => new Student{name = s.name, age = s.age}).ToList();

Console.WriteLine(String.Join(", ", copy1));

// Using ConvertAll()

var copy2 = list.ConvertAll(s => new Student{name = s.name, age = s.age}).ToList();

Console.WriteLine(String.Join(", ", copy2));

}

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Output:

[Olivia, 10], [Robert, 20], [John, 15]
[Olivia, 10], [Robert, 20], [John, 15]

C# had made it possible to write simpler and concise code. Starting with C#9, you can take advantage of the new with expression if your object contains many fields. The with expression can create a copy of any record with an arbitrary number of its init-only properties modified. The following code example demonstrates its usage:

using System;

using System.Linq;

using System.Collections.Generic;

class Student

{

public string name { get; set; }

public decimal age { get; set; }

public override string ToString() {

return "[" + name + ", " + age + "]";

}

public class Example

{

public static void Main()

{

var list = new List<Student> {

new Student{name = "Olivia", age = 10},

new Student{name = "Robert", age = 20},

new Student{name = "John", age = 15}

};

var copy = list.Select(s => s with { }).ToList();

Console.WriteLine(String.Join(", ", copy));

}

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Output:

[Olivia, 10], [Robert, 20], [John, 15]

2. Using `Clone()` method

Alternatively, you can implement your own Clone() method to facilitate a field-for-field copy of a class. Then you can simply loop over the list and clone each item by invoking the Clone() method, as shown below:

using System;

using System.Linq;

using System.Collections.Generic;

class Student

{

public string name { get; set; }

public decimal age { get; set; }

public Student Clone() {

return new Student {name = this.name, age = this.age};

}

public override string ToString() {

return "[" + name + ", " + age + "]";

}

public class Example

{

public static void Main()

{

var list = new List<Student> {

new Student{name = "Olivia", age = 10},

new Student{name = "Robert", age = 20},

new Student{name = "John", age = 15}

};

var copy = list.ConvertAll(s => s.Clone()).ToList();

Console.WriteLine(String.Join(", ", copy));

}

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Output:

[Olivia, 10], [Robert, 20], [John, 15]

3. Using `Serializable()` Method

Finally, you can use serialization to serialize an object into a MemoryStream and then deserialize it back. To indicate that instances of a class can be serialized, apply the SerializableAttribute attribute. The following example demonstrates the serialization of a List of objects.

using System;

using System.IO;

using System.Collections.Generic;

using System.Runtime.Serialization.Formatters.Binary;

[Serializable()]

class Student

{

public string name { get; set; }

public decimal age { get; set; }

public override string ToString() {

return "[" + name + ", " + age + "]";

}

public static class Extensions

{

public static List<T> Clone<T>(this List<T> list)

{

BinaryFormatter formatter = new BinaryFormatter();

MemoryStream stream = new MemoryStream();

formatter.Serialize(stream, list);

stream.Position = 0;

return (List<T>) formatter.Deserialize(stream);

}

public class Example

{

public static void Main()

{

var list = new List<Student> {

new Student{name = "Olivia", age = 10},

new Student{name = "Robert", age = 20},

new Student{name = "John", age = 15}

};

var copy = list.Clone();

Console.WriteLine(String.Join(", ", copy));

}

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Output:

[Olivia, 10], [Robert, 20], [John, 15]

That’s all about creating a deep copy of a List in C#.

Create a deep copy of a List in C#

1. Using Constructor

2. Using Clone() method

3. Using Serializable() Method

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2. Using `Clone()` method

3. Using `Serializable()` Method