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How to: Write a Copy Constructor (C# Programming Guide)

Unlike some languages, C# does not provide a copy constructor. If you create a new object and want to copy the values from an existing object, you have to write the appropriate method yourself.

Example

In this example, the Person class contains a constructor that takes as the argument another object of type Person. The contents of the fields in this object are then assigned to the fields in the new object.

class Person
{
    private string name;
    private int age;

    // Copy constructor.
    public Person(Person previousPerson)
    {
        name = previousPerson.name;
        age = previousPerson.age;
    }

    // Instance constructor.
    public Person(string name, int age)
    {
        this.name = name;
        this.age = age;
    }

    // Get accessor.
    public string Details
    {
        get
        {
            return name + " is " + age.ToString();
        }
    }
}

class TestPerson
{
    static void Main()
    {
        // Create a new person object.
        Person person1 = new Person("George", 40);

        // Create another new object, copying person1.
        Person person2 = new Person(person1);
        System.Console.WriteLine(person2.Details);
    }
}

Output

 
George is 40

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