converting array to custom list

Question

In my app I am writing data into a text file by converting a list into an array, later on I want to load it by converting it to the same list type and return it like that.

My code:

public abstract class PhoneBookCore
{
    protected string _group;

    public PhoneBookCore(string group)
    {
        this._group = group;
    }
}

public class Group : PhoneBookCore
{
    private List<PhoneBookCore> elements = new List<PhoneBookCore>();

    public List<PhoneBookCore> elementsList { 
         get { return new List<PhoneBookCore>(elements); } 
    }

    public Group(string name)
        : base(name)
    {
    }

class DataOptions
{
    public void Save(Group g)
    {
        string[] lines = g.elementsList.ConvertAll(p => p.ToString()).ToArray();
        File.WriteAllLines(path, lines);
    }

    public Group Load()
    {
        string[] buffer = File.ReadAllLines(path); // ----> How do I convert it back
                                                   //       to list of type group?

        return ;
    }
}

How do I convert it back to list of type group?

Why do you always create a new list in the elementsList property? Just return elements. — Tim Schmelter
– Tim Schmelter, Commented Feb 7, 2013 at 15:49
@TimSchmelter If I had to guess, I'd say to make the stored list read-only. — Theodoros Chatzigiannakis
– Theodoros Chatzigiannakis, Commented Feb 7, 2013 at 15:50
What is your question? If it's just what's in the comment, you could make it clearer (and you only need two lines of code to illustrate...) — Dan Puzey
– Dan Puzey, Commented Feb 7, 2013 at 15:51

Tim Schmelter · Accepted Answer · 2013-02-07 16:09:25Z

1

Maybe (assuming that you want to pass the whole line to the Group-constructor)

List<Group> allgroups = File.ReadLines(path)   
    .Select(l => new Group(l))
    .ToList();

Note that I've used File.ReadLines which returns a streaming IEnumerable<string> instead of a string[], you can also read all into memory at once with File.ReadAllLines.

But why do you always create a new list in the elementsList property? Just return elements.

Edit If you want to create one group and set the elementsList from the lines, you need to provide the setter of the property first:

private List<PhoneBookCore> _elementsList = new List<PhoneBookCore>();
public List<PhoneBookCore> ElementsList
{ 
    get { return _elementsList; }
    set { _elementsList = value; }
}

Then you can initialize and set the group on this way:

Group g = new Group(path); // i have no idea
g.ElementsList = File.ReadLines(path)
    .Select(l => new PhoneBookCore(l))
    .ToList();

return g;

edited Feb 7, 2013 at 16:09

answered Feb 7, 2013 at 15:52

Tim Schmelter

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2 Comments

darko Over a year ago

i want to return the list as type group

Tim Schmelter Over a year ago

Then you need to provide a setter for the elementsList property. Edited my answer.

thesheps · Accepted Answer · 2013-02-07 15:56:10Z

1

You're wanting to project each string item in your buffer list to a new PhoneBookCore instance. Since you're already using LINQ extensions, the following should suffice:

elementsList = buffer.Select(s => new PhoneBookCore(s)).ToList();

answered Feb 7, 2013 at 15:56

thesheps

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