Creating an immutable collection structure from existing hierarchical structure

Question

I have an object that stores hierarchical data. I have successfully been able to create the structure I need from a flat structure, but this required me to use List<> which isn't immutable (I want to use IReadOnlyList).

Now I can't really get my head around how I would create immutable lists based on these children lists. Can anyone guide me in the right direction?

The class looks like this:

public class ItemOrFolder
{
    public string Id { get; }

    public string Name { get; }

    public List<ItemOrFolder> Children { get; set; }    // Need to create immutable versions of these recursively

    private ItemOrFolder(string id, string name)
    {
        Id = id;
        Name = name;
    }

    public static ItemOrFolder Create(string id, string name)
    {
        return new ItemOrFolder(id, name);
    }
}

If Children is null, then it's an item, otherwise it's a folder, containing zero or more ItemOrFolder.

Answer 1

I can't find where Children property is set but you just need to add .ToImmutableList() to your list

item.Children = yourList.ToImmutableList();