[FIXED] How to properly return a list item for editing?

Issue

I created a class for convenient creation of a list that consists of different types of objects with a single interface.

A list item is created by calling a class method, the result of the method is a newly created object in the list for EDIT.

While this code works, I'm not sure if it's safe to return a list item to edit properties?

If not, how can you safely return an element from the list so that you can edit it.

var builder = new ElementBuilder();
var item = builder.AddText("abc");

// Edit new reference element property, should be stored in "builder" variable
item.Bold = true;

.....

// Pass builder instance with added items to other place

// If we do something like this with added values on above
var x = builder.First() as TextElement; 
Console.WriteLine(x.Text);
Console.WriteLine(x.Bold);

// Should output:
abc
true

public class ElementBuilder
{

    private List<IElement> elements =  new List<IElement>();;

    public TextElement AddText (string text)
    {
        var item = new TextElement (text);
        elements.Add(item);
// RETURNING to edit properties, updates of returning should affect to list item
        return _elements.First(x => x == item);
    }

    public ImageElement AddImage (string imageUrl)
    {
        var item = new ImageElement (imageUrl);
        elements.Add(item);

// RETURNING to edit properties, updates of returning should affect to list item
        return _elements.First(x => x == item);
    }

    public IElement First() 
    {
        return elements.First();
    }

    .....
}

Solution

if it's safe to return a list item to edit properties?

yeah, it is safe because what code is doing is it returns the reference to newly created item:

var item = new TextElement (text);

There are really nice posts how reference types work:

• Value and Reference types confusion
• Reference type in C#

In addition, it is possible to avoid iteration of the whole collection by returning item, not using First() method:

public IElement AddText (string text)
{
    var item = new TextElement (text);
    elements.Add(item);
    
    return item;
}

Because when you Add item into collection, then newly created item will be added at the end of list. So, First() method will iterate the whole List<T> to find your item. It can be seen in source code of First() method.

Answered By - StepUp

Answer Checked By - Terry (PHPFixing Volunteer)