C# Dynamic list of objects

Question

i have a small entity "Category"

Id
Name 
Parent_id

I want to override the ToString() with a string of all parents of the item and i dont know how many parents the item have.

Example: (pseudo code)
Item1 =>  Id = 1, Name = Computers, Parent_id = null 
Item2 =>  Id = 2, Name = Laptops  , Parent_id = 1
Item3 =>  Id = 3, Name = Acer     , Parent_id = 2

On the output from Item3.ToString() i want the result to be "Computers > Laptops > Acer" . And i need it to be dynamic so i dont know how many steps it should take... Any fresh idéas?

Answer 1

You need to do this recursively:

public overrides string ToString()
{
    string build = parent.ToString();
    if (!String.IsNullOrEmpty(build)) build += " > ";
    build += Name;
    return build
}

Something along the lines of the above should do it - each Entity will call ToString on its parent so you get the list of all entities in the hierarchy. This will work however deep the hierarchy gets (within reason).

Note: you'll need a reference to the parent to do this, either you can use a property, or you can look the entity up using the parentid property you've already got.

Answer 2

First, you need to add the parent item itself (not just the ID) to every item, then it should be easy enough with simple loop:

public override string ToString()
{
    List<string> names = new List<string>();
    names.Add(this.Name);
    Category parent = this.Parent;
    while (parent != null)
    {
        names.Add(parent.Name);
        parent = parent.Parent;
    }
    names.Reverse();
    return string.Join(" > ", names);
}

Answer 3

public class Category
{
    public int Id { get; set; }
    public string Name { get; set; }
    public Category Parent { get; set; }

    public override string ToString()
    {
        return Parent == null 
            ? Name
            : string.Format("{0} > {1}", Parent, Name);
    }
}

Usage:

item1 = new Category{Id = 1, Name = "Computers"};
item2 = new Category{Id = 2, Name = "Laptops", Parent = item1};
item3 = new Category{Id = 3, Name = "Acer", Parent = item2};

Debug.Print(item3.ToString());
Debug.Print(item2.ToString());
Debug.Print(item1.ToString());

Result:

Computers > Laptops > Acer
Computers > Laptops
Computers