Question

How do I copy (and insert) the last object in a list.

public class MyObject
{
    public string first {get;set;}
    public string second {get;set;}
}

List<MyObject> list = new List<MyObject>();
list.Add(new MyObject{first = "one", second = "two"});
list.Add(new MyObject{first = "here", second = "there"});
list.Add(new MyObject{first = "car", second = "plane"});

MyObject newObj = new MyObject();
list.Add(newObj);

It seems as if the last two objects in the list is references to the same object. How do I create a new object that is still a copy of the last object in the list?

EDIT
I shouldn’t have simplified my problem and the class (not actually called MyObject) for this example. It’s actually much larger with more children objects and lists.

Answer 1

There are two common ways:

(1) Write a Copy Constructor for the MyObject class, and use it to make a copy of the object, then insert the copy.

(2) Or write a Clone method for the MyObject class, and use that to make a copy, then insert the copy.

However, in the code you presented, you are NOT making a copy of anything, nor are you inserting into the list a reference to an existing object.

Here’s an example how you can do it:

public class MyObject
{
    public string first
    {
        get;
        set;
    }
    public string second
    {
        get;
        set;
    }

    public MyObject DeepClone()
    {
        return new MyObject{ first = this.first, second = this.second;}
    }
}

// Then you can do this:

List<MyObject> list = new List<MyObject>();
list.Add(new MyObject{first = "one", second = "two"});
list.Add(new MyObject{first = "here", second = "there"});
list.Add(new MyObject{first = "car", second = "plane"});

list.Add(list[list.Count-1].DeepClone());