C# copy constructor

Question

I apologize for asking something that is probably too basic for C# folks. I'm mostly doing my coding in C++.

So if I want to write an assignment constructor for my class, how do I do that? I have this so far, but it doesn't seem to compile:

public class MyClass
{
    public string s1;
    public string s2;
    public int v1;

    public MyClass()
    {
        s1 = "";
        s2 = "";
        v1 = 0;
    }

    public MyClass(MyClass s)
    {
        this = s;    //Error on this line
    }
}


MyClass a = new MyClass();
MyClass b = new MyClass(a);

Answer 1

You can't assign the class itself - a constructor of that form will typically copy members of the other class:

public MyClass(MyClass s)
{
    this.s1 = s.s1;
    this.s2 = s.s2;
    this.v1 = s.v1;
}

That gives you a "copy" by value of the items in your other class. If you want to have the reference shared, you can't do that, but you wouldn't need a constructor - assigning the variables works fine for that:

var orig = new MyClass();
var referencedCopy = orig; // Just assign the reference

Answer 2

What you are trying to do can be achieved using Clone

public class MyClass : ICloneable
{
    public string s1;
    public string s2;
    public int v1;

    public MyClass()
    {
        s1 = "";
        s2 = "";
        v1 = 0;
    }

    public Object Clone()
    {
        return this.MemberwiseClone();
    }
}

Consuming:

MyClass a = new MyClass();
MyClass b = (MyClass)a.Clone();

Answer 3

You can't assign this in a class type. The best way is probably to create another constructor and call that:

public MyClass() : this(string.Empty, string.Empty, 0) { }

public MyClass(MyClass s) : this(s.s1, s.s2, s.v1) { }

private MyClass(string s1, string s2, int v1)
{
    this.s1 = s1;
    this.s2 = s2;
    this.v1 = v1;
}